排序方式: 共有67条查询结果,搜索用时 15 毫秒
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Boris M. Epelbaum Kiyoshi Shimamura Satoshi Uda Junichi Kon Tsuguo Fukuda 《Crystal Research and Technology》1996,31(8):1077-1084
The μ-PD method originally developed for oxide crystals has been modified and applied for filamentary silicon crystal growth. Our main modification of μ-PD method is concerned with an arrangement of melt permeable feeder which is inserted into the nozzle. The feeder finishes by a sharp tip the diameter of which (is almost the same as that of the desired semiconductor fiber, i.e., less than 150 μm. Silicon fibers were grown from the small liquid pool at the end of the feeder. Three types of crucible-die arrangement were designed and tested. The best results were obtained with the help of inclined insert made of graphite fibers because of its ability to quench oscillations and longer operation life. Fiber crystals, 100 μm in diameter and 70 mm in length, have been grown successfully. Small meniscus stability, operating limits of μ-PD method and silicon carbide formation during the growth process are discussed. 相似文献
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Mark Lenkewitz Evgeny Epelbaum H. -W. Hammer Ulf-G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2013,49(2):1-11
We calculate the electromagnetic neutral pion production off tri-nucleon bound states (3H, 3He) at threshold in chiral nuclear effective field theory to fourth order in the standard heavy baryon counting. We show that the fourth-order two-nucleon corrections to the S-wave multipoles at threshold are very small. This implies that a precise measurement of the S-wave cross section for neutral pion production off 3He allows for a stringent test of the chiral perturbation theory prediction for the S-wave electric multipole $E_{0+}^{\pi^0 n}$ . 相似文献
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Nogga, Timmermans and van Kolck recently argued that Weinberg’s power counting in the few–nucleon sector is inconsistent and requires modifications. Their argument is based on the observed cutoff dependence of the nucleon–nucleon scattering amplitude calculated by solving the Lippmann–Schwinger equation with the regularized one–pion exchange potential and the cutoff Λ varied in the range Λ = 2 . . . 20 fm?1. In this paper we discuss the role the cutoff plays in the application of chiral effective field theory to the two–nucleon system and study carefully the cutoff–dependence of phase shifts and observables based on the one–pion exchange potential. We show that (i) there is no need to use the momentum–space cutoff larger than Λ ~ 3 fm?1; (ii) the neutron–proton low–energy data show no evidence for an inconsistency of Weinberg’s power counting if one uses Λ ~ 3 fm?1. 相似文献
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H. Witała J. Golak R. Skibiński K. Topolnicki H. Kamada E. Epelbaum W. Glöckle H. Krebs W. N. Polyzou A. Nogga 《Few-Body Systems》2013,54(7-10):897-902
Faddeev calculations using the chiral three-nucleon force in next-to-next-to-next-to-leading-order show that this force is too weak to provide an explanation for the low-energy A y puzzle. The large discrepancy between data and theory for the neutron–neutron quasi-free-scattering cross section in low energy neutron–deuteron breakup requires a modification of the ${^{1}S_0}$ neutron–neutron force. We discuss the consequences that a bound ${^{1}S_0}$ state of two neutrons has on neutron–deuteron scattering observables. At higher energies we compare the solutions of the non-relativistic three-nucleon Faddeev equations with three-nucleon force included to the solutions of its Poincaré invariant version. 相似文献
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V. V. Kochurikhin K. Shimamura B. M. Epelbaum H. Takeda T. Fukuda 《Crystal Research and Technology》1998,33(1):65-70
The automatic diameter control system using the results of spectral analysis of weight sensor data as a criterion for the amount of feedback tuning was applied successfully for the growth of La3Ga5SiO14 single crystals. The developed method enabled to determine timely the appearance of oscillations in the control system and to adapt the amplification factor automatically for the maintenance of stable crystal shape. Furthermore, the developed system made it possible to estimate the formation of a second phase at a very early stage. 相似文献