共查询到20条相似文献,搜索用时 9 毫秒
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Jue-ping LIU 《理论物理通讯》1987,8(2):239-253
The QCD sum rules for the proton. mass,the n-p mass ratio and the optimal observation point are analysed, which can greatly improve the precision of the theoretical results. If we take = and mu/(mu+md)-=0.35 which agree with the values from SVZ and current algebra[1,2],we obtain Mp=935.86MeV and Mp/Mn=0.99871 which coincide quite well with experimental values.The isospin behavior of light quarks is investigated. It shows that the isospin symmetry of the light quark condensates is very good up to the low-energy region (about 500MeV),and that the n-p mass difference can be originated from the u-and d-quark mass differences. 相似文献
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The independent particle approximation is used to treat the bound state problems in the quark model. The solution for meson states obtained in this approximation is the same as that obtained from the Bethe-Salpeter equation. The solution for the baryon states is also obtained. The mass spectra of mesons and baryons determined from these equations are in agreement with the experiment. 相似文献
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GPS“射线打靶”模式高效数值方法的研究及其并行实现 总被引:3,自引:0,他引:3
全球定位系统(GPS)"射线打靶法"是GPS MET(气象)资料变分同化中一种自成一体的观测算子,由于其计算量非常巨大而一直没能在资料同化中得到使用.为了减少该观测算子的计算量,针对GPS射线轨迹方程为一可分Hamilton系统的特点,采用二阶经济辛格式求解,与经典的四阶Runge Kuntta法相比,不仅计算准确度没有降低甚至有所改善,而且节省近4倍的计算时间.同时进一步研究了改进后的GPS"射线打靶"模式的并行实现. 相似文献
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By introducing a series of mathematical symbols and phase quantization condition, we give a new approach to the phase operator, which is defined directly in the conventionally-used infinite-dimensional state spaces. Properties of the phase operator and its expressions in some widely-used representations are given. As an example, phase properties of coherent states are analyzed based on this definition. 相似文献
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中微子的静止质量及其在物理学和宇宙学上的意义 总被引:5,自引:0,他引:5
简要地介绍了中微子的发现历史及其基本特性,着重介绍了Super-Kamiokande中微子天文台大气中微子实验和太阳中微子实验的基本原理及其最新实验结果,对中微子的静止质量在太阳中微子失踪问题、粒子物理学和宇宙学上的意义作了讨论,指出了与中微子静止质量相关的3个有待解决的问题。 相似文献
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QCD PERTURBATION THEORY AND NUCLEI (1) THE ENERGY SHIFTS OF HADRENS AND HADRONS MASS DIFFERENCE MASS DIFFERENCE 下载免费PDF全文
QCD perturbation theory for confined quarks and gluons (inhadrons) is discussed.Based on the equivalent potential for the quark-gluon interaction derived, the energyshifts of hadrons and hadron mass difference in MIT bag (cavity) model and correcpond-ing approximation of the w. f. with Gassian form are calculated. 相似文献
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水分布对蒸发式冷凝器传热传质的影响 总被引:1,自引:0,他引:1
蒸发式冷凝器具有节水、节能、结构紧凑等优点而在工业制冷等领域得到了广泛的应用.在蒸发式冷凝器性能测试实验平台基础上,测试了水流参数如喷淋密度和水温对蒸发式冷凝器传热传质性能的影响.结果表明,在满足最小喷淋密度后,喷淋密度对蒸发式冷凝器传热传质性能影响很小;在稳定的操作条件下,蒸发式冷凝器水盘中的水温可以保持恒定;循环冷却水水温降低1.1~2.0℃,在相同的操作条件下,蒸发式冷凝器传热传质系数可以分别提高7.2%~16.9%和34.5%~63.4%. 相似文献
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当温度超过1 000 ℃时,人造金刚石中的金属触媒包裹体,在形态、结构和成份上都将发生改变,并且这种变化会在金刚石晶格内造成尺寸更大的缺陷区域,因此在表面氧化不起决定性作用的情况下,金属触媒包裹体的这种变化,就成了导致金刚石强度下降的最直接的原因。我们对在氩气保护下、不同温度处理的一系列人造金刚石样品进行了强度测量,并用SEM、X射线衍射及光学显微镜等手段观测了金刚石断裂表面上的包裹体及其形态变化。我们的实验结果证实了上述结论。我们还发现,金属触媒包裹体的存在极大地影响着金刚石的热稳定性,它们使金刚石在1 000 ℃左右即可向石墨转化。 相似文献
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本文由光学变量算符的线性变换将文献[3]建立的光学矩阵与光学算符的关联方程加以推广,得到光学广义关联方程;又引入本征光学变量算符使其简化成约化光学广义关联方程;从而获得由关联方程求光学点扩散算符的“模拟单透镜成象光路”的普适解法。
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We present a simple and crude model of galaxies consisting of baryons and neutrinos with spherical symmetry. The baryon matter is rotatinq. in the central region of the galaxy as a nucleus. If the rotational curve of the heavy matter is known from the observational data, then the gravitational potential, and therefore the density distribution in this region, can also be obtained. This enables us to estimate the mass and the radius of the neutrino halo. Furthermore, the condition on the interface of the nucleus-halo will set an upper bound on neutrino mass. If the corresponding parameters duoted in Ref.[10] are adopted, then a value of ≤20eV. for the neutrino mass is obtained. By choosing mv=15eV and a parameter in the rotational curve n=4, one can deduce that neutrino halo radius is about four times the heavy matter radius, and the total mass of neutrinos is about 14 times that of baryons. It seems, that these results are not in contradiction with the observations on the missing mass of the galaxies[6]. 相似文献
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蔬菜种子干燥中种皮的效应与优化传热传质机理 总被引:4,自引:1,他引:3
1前言含水率大的种子在贮存过程中极易发生劣变,使发芽力与发芽势降低山。种子干燥是一个复杂的传热传质过程,而且还涉及到生命力保存的问题。虽然种子的形态存有差异,但是种子的基本结构都是一致的。一般都由胚、胚乳和种皮三部分组成。种皮对种子具有保护与协调的功能,其透气性与透水性决定了种皮是种子与周围环境进行质量与能量交换的必经之路。为此本文综合种子的生物生理特性研究了蔬菜种子干燥中种皮的作用,并结合种皮的生物学功能探讨了优化传热传质的机理。2种皮对干燥的影响实验装置见文献[2],采用在线测量的方法可连续检… 相似文献
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给出了一个量子Hamiltonian系统存在非零绝热几何位相的必要条件:不同时刻的Hamiltonian量不可对易。我们指出,约束条件=0唯一地确定了归一化本征态矢|n′(t)>在不同时刻的位相关系,并且在此基础上讨论了非零绝热几何位相存在的充分必要条件:当=0时,|n′(T)>≠|n′(0)>;给出了计算绝热几何位相的普遍的时间积分公式。作为该公式的应用,计算了Solem和Biedenham讨论过的自旋1/2系统的绝热几何位相,并且指出,Solem和Biedenham所遇到的问题源于本征态矢在参数空间中的多值性。
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