885 resultados para Gauss Reciprocity
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In this paper we present a robust face location system based on human vision simulations to automatically locate faces in color static images. Our method is divided into four stages. In the first stage we use a gauss low-pass filter to remove the fine information of images, which is useless in the initial stage of human vision. During the second and the third stages, our technique approximately detects the image regions, which may contain faces. During the fourth stage, the existence of faces in the selected regions is verified. Having combined the advantages of Bottom-Up Feature Based Methods and Appearance-Based Methods, our algorithm performs well in various images, including those with highly complex backgrounds.
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研究了掺Yb3+硅酸盐玻璃的吸收光谱和发射光谱. 采用Fuchbauer—Ladenburger(F-L) 和 Reciprocity Method(RM)两种方法计算和探讨了Yb3+的积分吸收截面和受激发射截面及荧光寿命等光谱参数. 结果表明, 相同厚度下这些参数随Yb2O3 掺杂浓度的增加而增大,且在Yb2O3 浓度为1.5mol%时取得最大值,在样品厚度为2mm 时荧光寿命最大(1.06 ms);Yb3+基态再吸收造成采用两种方法计算的发射面积存在差值,比较发现采用RE 方法计算Yb3+的受激发射截面较为合理.
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在兰州重离子加速器国家实验室(HIRFL)放射性次级束流线(RIBLL)上,用束流透射法测量了丰中子奇异核17B与C靶反应的总截面.假定17B具有15B(核芯)+2n结构,采用Gauss+HO形式的密度分布和零力程Glauber模型进行计算的结果可以很好地拟合实验数据,并得出17B的密度分布有一个很大的弥散,表明17B是双中子晕核.
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利用HIRFL提供的50MeV/u的~(13)C束流轰击Be靶,通过RIBLL选择出放射性核素~(11)Li.实验采用透射法测量了25—45MeV/u的~(11)Li在~(28)Si靶上的反应总截面.采用双参数Gauss密度分布形式,利用Glauber模型很好地拟合了高能和中能区的~(11)Li实验数据,并从密度分布中提取了核的物质均方根半径.
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在兰州重离子加速器国家实验室(HIRFL)放射性次级束流线(RIBLL)上,用束流透射法测量了丰中子奇异核17B与C靶反应的总截面.假定17B具有15B(核芯)+2n结构,采用Gauss+HO形式的密度分布和零力程Glauber模型进行计算的结果可以很好地拟合实验数据,并得出17B的密度分布有一个很大的弥散,表明17B是双中子晕核.
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We consider the Randall-Sundrum brane-world model with bulk-brane energy transfer where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. It is remarkable that these curvature terms will not change the dynamics of the brane universe at low energy. Parameterizing the energy transfer and taking the dark radiation term into account, we find that the phantom divide of the equation of state of effective dark energy could be crossed, without the need of any new dark energy components. Fitting the two most reliable and robust SNIa datasets, the 182 Gold dataset and the Supernova Legacy Survey (SNLS), our model indeed has a small tendency of phantom divide crossing for the Gold dataset, but not for the SNLS dataset. Furthermore, combining the recent detection of the SDSS baryon acoustic oscillations peak (BAO) with lower matter density parameter prior, we find that the SNLS dataset also mildly favors phantom divide crossing.
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The neutron-rich nucleus Li-11 is separated by the radioactive ion beam line RIBLL at HIRFL from the breakup of 50MeV/u C-13 on Be target. The total reaction cross sections for Li-11 at energies range from 25 to 45MeV/u on Si target have been measured by using the transmission method. The experimental data at high and low energies can be fitted well by Glauber model using two Gauss density distribution. The matter radius of Li-11 was also deduced.
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We study the relation between the thermodynamics and field equations of generalized gravity theories on the dynamical trapping horizon with sphere symmetry. We assume the entropy of a dynamical horizon as the Noether charge associated with the Kodama vector and point out that it satisfies the second law when a Gibbs equation holds. We generalize two kinds of Gibbs equations to Gauss-Bonnet gravity on any trapping horizon. Based on the quasilocal gravitational energy found recently for f(R) gravity and scalar-tensor gravity in some special cases, we also build up the Gibbs equations, where the nonequilibrium entropy production, which is usually invoked to balance the energy conservation, is just absorbed into the modified Wald entropy in the Friedmann-Robertson-Walker spacetime with slowly varying horizon. Moreover, the equilibrium thermodynamic identity remains valid for f(R) gravity in a static spacetime. Our work provides an alternative treatment to reinterpret the nonequilibrium correction and supports the idea that the horizon thermodynamics is universal for generalized gravity theories.
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We derive the generalized Friedmann equation governing the cosmological evolution inside the thick brane model in the presence of two curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. We find two effective four-dimensional reductions of the generalized Friedmann equation in some limits and demonstrate that the reductions but not the generalized Friedmann equation can be rewritten as the first law of equilibrium thermodynamics on the apparent horizon of thick braneworld.
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核反应总截面是描述原子核反应基本特征的一个重要的物理量,从中可以得到有关核反应、核结构和核内核子分布的信息。利用透射法测量核的反应总截面对于模型没有依赖性,因而得到的结果更加可靠。在兰州放射性束流线(RIBLL)上利用透射法测量了17B与C、Pb靶的反应,得到了17B与C、Pb的反应总截面和去除双中子截面,同时首次尝试用CLOVER探测器测量与碎片符合的γ能谱。利用半经验的Shen公式可以很好地拟合稳定核的反应总截面的实验结果,但是并不能很好地描述17B的实验结果,说明17B具有奇异结构。采用描述不稳定核的多种密度分布形式代入零力程的Glauber模型计算17B与C的反应总截面,并与实验结果进行了比较。发现采用Skyrme-Hatree-Fock(SHF)、双Gauss、Gauss+HO计算的密度分布形式都能够很好地拟合整个能区内的实验结果。通过各种密度分布形式提取了17B的核子密度分布,发现17B的中子密度分布有很大的弥散,并证实了17B是由核芯15B加两个价中子组成的晕结构。将Skyrme-Hatree-Fock(SHF)、双Gauss、Gauss+HO密度分布形式,输入Glauber模型与实验结果比较,提取了17B的物质均方根半径,不同密度分布提取的均方根半径值在实验误差范围内一致,也进一步验证了17B的晕结构。采用Woods-Saxon势来描述17B核外的价中子在核芯中形成的势场,通过解薛定鄂方程来求解价中子处于特定轨道的波函数。假设17B核外的价中子处于纯的s分波和d分波都不能很好地和实验结果符合。所以认为核外的价中子应该是混合组态,通过拟合实验结果求解出s分波谱学因子的值,证明核外的价中子处在2s1/2轨道的几率更大
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核反应总截面是描述原子核反应基本特征的一个重要的物理量,从中可以得到有关核反应、核结构和核内核子分布的信息。在由放射性束所产生的奇异核结构与各种反应机制的研究中,反应总截面更是具有特殊的重要性。具有奇异核结构的核的一个典型物理现象就是其反应总截面要比稳定核大得多,I.Tanihata等人最早就是通过对放射性束流的相互作用截面的测量发现了具有奇异结构的核-中子晕核。由于反应截面的测量对探测器的要求不高,而且数据分析过程相对较为简单,因此反应截面的测量已经成为放射性束物理研究的一个非常重要的实验手段。目前,奇异核研究的重点在丰中子一侧,理论预言的很多中子晕核如8He、11Li、11、14Be、15、17、19C、等已经从实验上得到证实,而理论预言的质子晕核目前只有8B得到实验证实,其他的核实验数据较少或相互矛盾,无法作出准确的结论。12N就是其中之一,理论学家认为其具有质子晕结构;而实验数据主要集中在的反应截面测量上,实验数据较少又相互矛盾或不肯定,不能得出确切结论。因此,进一步开展研究是十分必要和有意义的。考虑到以上因素,充分利用兰州放射性束流线现有的实验条件,我们采用束流透射法测量了中能区多个能量点12N、11C、12B与Si靶的反应总截面和12N去质子截面。同时用CLOVER探测器测量与碎片符合的γ能谱。利用透射法测量核的反应总截面对于模型没有依赖性,因而得到的结果更加可靠。利用Shen公式和采用各种密度分布形式的零力程Glauber模型计算了12N、11C、12B的激发函数并与实验结果比较,提取了12N、11C、12B的密度分布与核半径,对12N去质子截面作了简单分析。使用Shen公式拟合实验数据时发现,Shen公式在整个能区范围内基本上可以很好的拟合12B、11C的反应数据,但Shen计算得到的12N的反应总截面与实验测量值有明显的差异,计算结果偏小。在使用Glauber模型拟合实验数据之前,分别使用有限力程和零力程Glauber模型拟合了12C+12C的实验数据。在计算时,两种Glauber模型输入的密度分布采用Gauss密度分布形式。结果显示,使用零力程Glauber模型可以更好的拟合实验数据。分别使用高斯密度分布、HO密度分布、双参数费米密度分布、SHF模型计算得到的密度分布、基于少体模型的Gauss+尾巴密度分布形式代入零力程Glauber模型拟合实验数据。对于12B、11C、12C,这些密度分布形式代入零力程Glauber模型计算得到的激发函数曲线在整个能区范围内都可以很好的拟合实验数据。但是对于12N,只有基于少体模型的Gauss+尾巴密度分布形式代入零力程Glauber模型计算得到的激发函数曲线可以拟合实验结果。其他的密度分布形式计算得到的激发函数曲线明显低于实验数据。提取的12B、11C、12N均方根半径显示,12N的核半径明显大于其镜像核12B及其周围的核素。对12B、11C、12N的分析结果表明:12N的密度分布形式和稳定核有明显的不同,最后一个质子的密度分布具有很大的弥散,其可能具有奇异结构。对12N去质子截面的简单分析也表明了这一点
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HIRFL is a tandem cyclotron complex for heavy ion. On the beam line between SFC and SSC, there is a stripper. Behind it, the distribution of charge states of beam is a Gauss distribution. The equilibrium charge state Q_0 is selected by 1BO2(a 50° dipole behind the stripper) and delivered to SSC. One of two new small beam line (named SLAS) after 1B02 will be builded in or der to split and deliver the unused ions of charge states (Q_0 ± n) to aspecific experimental area. Q_0 ± n ions are septumed and separated from initial(Q_0) ion beam by two septum magnets SM1, SM2. The charge state selected by SM1 will be Q_0 ± 1(6 ≤ Q_0 < 17), Q_0 ± 2(17 ≤ Q_0 < 33) and Q_0 ± 3 (Q_0 ≥ 33) forming a beam in one of the two possine new beam line with the stripping energy of (0.2 to 9.83 Mev/A), an emittance of 10π mm.mrad in the two transverse planes and an intensity ranging from 10~(11) pps for z ≤ 10 to some 10~5 pps for the heaviest element. Behind SM2, a few transport elements (three dipoles and seven qudrupoles) tra nsport Q_0 ± n beam to target positions T1, T2 (see fig. 1) and generate small beam spots (φ ≤ 4mm, φ ≤ 6mm). The optics design of the beam line has been done based on SLAC-75 (a first and second - order matrix theory). beam optics calculation has been worked out with the TRANSPORT program. The design is a very economical thinking, because without building a new accelerator we can obtain a lower energy heavy ion beam to provide for a lot of atomic and solid state physical experiments
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直到八十年代中期,人名才发现耗散反应激发函数中存在振荡结构这种新现象。通过对激发函数振荡结构能量自关联函数的研究是获得复合核能级宽度的一个重要手段,Brick推广了Ericson的复合核统计理论,并成功地用于分析耗散反应激发函数振荡结构的研究,提取相应的能量相关宽度Г。本文报道了19F+51V耗散反应激发函数振荡结构的实验研究结果,用能级部分重叠模型对角动量相干引起的截面涨落、能量自关联函数进行了计算分析。实验中采用ΔE-E粒子鉴别方法和飞行时间TOF测量技术队102.25Mev~109.5Mev19F+51V反应类弹产物同时进行电荷和质量鉴别。首次在各个元素、同量异位素(质量数A为常数)和同位素的耗散反应激发函数中观察到振荡结构,并进一步证实了反应产物的各个出射道之间存在着相关。检验了用小角度弹性散射计数做相对归一对激发函数振荡结构研究可能造成的影响。分别采用能量自关联函数方法和谱密度方法提取了各个激发函数的能量相关宽度Г,其值大小为~350kev,并与出射道的电荷数Z、质量数A和中质比N/Z有很大的依赖关系,表明出射产物与入射弹核的差别越打所需的反应时间久越长。首次得到了Г随N/Z值变化的趋势,Г随N/Z的分布为Gauss型,通过分析分布的宽度得到其大小随相互作用时间的增长而线性增大的结果,并进一步提取了电荷扩散系数,证实了反应系统已达到电荷平衡。Г的数值随出射角的增大有减小的趋势。双核系统的转动造成了Г随出射角的变化关系,实验提取的双核系统平均角速度发生了较强的阻尼。用能级部分重叠模型在适当的精度内对激发函数和能力自关联函数进行了模拟。计算分析说明入射道的动能大多数转化为双核系统的转动能,只有较少部分转化为双核系统的内禀激发能,双核系统被激发到能级密度不太大的区域,能级之间的部分重叠引起截面的振荡行为。入射道角动量的相互干涉、双核系统能级的部分重叠和出射道的相互关联使得耗散反应的激发函数表现出其特有的规律性。
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Ocean acoustic propagation and reverberation in continental shelf regions is often controlled by the seabed and sea surface boundaries. A series of three multi-national and multi-disciplinary experiments was conducted between 2000-2002 to identify and measure key ocean boundary characteristics. The frequency range of interest was nominally 500-5000 Hz with the main focus on the seabed, which is generally considered as the boundary of greatest importance and least understood. Two of the experiments were conducted in the Mediterranean in the Strait of Sicily and one experiment in the North Atlantic with sites on the outer New Jersey Shelf (STRATAFORM area) and on the Scotian Shelf. Measurements included seabed reflection, seabed, surface, and biologic scattering, propagation, reverberation, and ambient noise along with supporting oceanographic, geologic, and geophysical data. This paper is primarily intended to provide an overview of the experiments and the strategies that linked the various measurements together, with detailed experiment results contained in various papers in this volume and other sources
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电子计算机应用于分光光度法为同时分析相互干扰的多组分体系开辟了一个新的研究领域。文献报道的线性规划、因素轮换优选、因子分析、正交分解及可变误差多面体法已显示了计算分光光度法的优越性。在所报道的工作中,测定某单组分的吸光常数时,大都没有其它组分共存,依据α=A/bc来计算其吸光常数。但结果产生较大的误差。本文以化学性质极其相似的La、Ce、Pr、Nd、Sm为分析对象,采用五个已知组成的标样,通过全选主元的Gauss消去法求得单组分的吸光常数。据此再用可变误差多面体法求解样品中各组分的浓度。实践证明,此法不仅减小了实验误差和手工计算时间,而且考虑了组分间的相互作用,所以获得比较准确的结果。可变误差多面体法也是解决这类问题更为合适的方法。