共查询到19条相似文献，搜索用时 281 毫秒
1.
运用调和序列和活动标架研究复格拉斯曼流形G(2,5)中的调和2-球面.通过S2上全纯微分形式的构造,简化G(2,5)中沿调和2-球面的活动标架,并且给出高斯曲率的上界估计. 相似文献
2.
采用高温固相法在1400℃合成了新型橙红色Sr_2MgAl_(22)O_(36):Sm~(3+),M~+(M=Li,Na)荧光粉。通过X射线衍射仪及扫描电镜对样品进行表征。XRD测量结果表明,所制备的样品为MgAl_(22)O_(36)纯相。激发光谱显示,样品在330~480nm范围内能得到有效激发。在405nm激发下,发射光谱由三个锐锋组成,其峰值位于562nm(4G5/2→6H5/2),595nm(4G5/2→6H7/2),640nm(4G5/2→6H9/2),其中595nm处峰值最大。文章研究了Sm~(3+)掺杂浓度及电荷补偿剂对荧光粉发光性能的影响。Sr_(2-2x)Sm_xM_x(M=Li,Na)Mg Al22O36的发光强度随着Sm~(3+)浓度的增大,先增大后减小,最佳Sm~(3+)的掺杂量为x=0.05。Sr_(2-2x)Sm_xNa_xMgAl_(22)O_(36)的发光强度高于Sr_(2-2x)Sm_xLi_xMgAl_(22)O_(36)。 相似文献
3.
得到Dressing作用的一些性质 ,证明标准的n uniton扩张解在Dressing作用下仍然是标准的n uniton扩张解 ,因而Dressing作用保持有限调和映射的极小uniton数不变 (后面的结论已被Guest和Ohnita证明 ) .特别证明对于全纯映射 ,Dressing作用仅与群元素在零点值有关 .此性质表明Loop群在全纯映射上的作用与复线性群在复Grassman nians上的标准作用是等价的 . 相似文献
4.
利用同步辐射光和反射飞行时间质谱,研究了丙烯酸甲酯9.0~15.5 eV能量范围的真空紫外光电离和光解离.实验测量丙烯酸甲酯的光电离质谱和解离碎片离子m/e=86(C4H6O+2), 85(C4H5O+2), 59(C2H3O+2), 58(C3H6O+), 55(C3H3O+), 42(C3H+6), 31(CH3O+), 27(C2H+3), 和15(CH+3)的光电离效率曲线.并利用量子化学从头算(G3),计算碎片离子的能级,推测它们的解离通道.计算的电离能和出现势与实验结果符合很好.结果表明,丙烯酸甲酯的光电离解离通道以单键断裂反应为主. 相似文献
5.
柴丽霞 《内蒙古科技与经济》2004,(22):63-63
1 包头市可利用供水水源状况包头市区可利用的供水水源有 :地下水资源、水库水和黄河水。包头市及近郊范围内的地下水多年平均补给资源量为 1 .2 6× 1 0 8m3/a;水库可向城市提供 5× 1 0 4 m3/d,作为城市自来水公司季节性调节水源 ;目前包头市在黄河昭君坟段和磴口段取黄河水量为 1 .5 7× 1 0 8m3/a作为城市供水 (包括包钢用水 )。综合地下水和地表水 ,现包间市区可利用的水资源量为 3× 1 0 8m3/a左右 (含 1× 1 0 8m3/a的农业用水 ,可作为城市供水资源量约为 2× 1 0 8m3/a左右 )。 1 996年城市总供水量为 2 .5 5× 1 0 8m3/a,地下水已… 相似文献
6.
探讨老年人扩张型心肌病 ( DCM)的临床特征并与青年人 DCM进行比较 .通过临床观察对 80例老年人和 140例青年 DCM的临床资料进行对比分析 .结果发现 :( 1)老年组醛固酮值( 30 4 .8± 69.1)较青年组 ( 2 13.3± 54.5,pmol/ L)明显增高 ( P<0 .0 5) ,老年组 T3和 FT3值 ( 0 .78± 0 .2 1,2 .87± 0 .73)较青年组 ( 1.2 6± 0 .33nmol/ L ,3.55± 0 .64pmol/ L )明显降低 (均为 P<0 .0 1) ;( 2 )老年组室性心律失常发生率 ( 61.3% )较青年组 ( 92 .1% )低 ( P<0 .0 1) ;( 3)老年组低血钾、低血镁发生率高 (分别为 51.3%和 2 7.5% ) ,对洋地黄敏感性增加 ,易发生洋地黄中毒( 2 8.8% ) ;( 4 )老年组的病程 [( 11.0± 4 .7)年 ]和平均生存期 [( 6.9± 4 .2 )年 ]均较青年人 [( 5.2±2 .5)和 ( 3.4± 2 .7)年 ]长 (均为 P<0 .0 5) ;( 5)老年组的主要死因是充血性心力衰竭 ( 78.9% ) ,青年组则为恶性心律失常 ( 61.9% ) .结论为老年人 DCM的预后比青年人相对要好 ;老年人 DCM常伴低 T3综合征 ;心力衰竭、电解质失衡及交感神经兴奋是老年人 DCM室性心律失常的主要原因 相似文献
7.
《百科知识》2006,(23)
眼光科学永远需要实事求是鱼儿鸟儿受害后最高科学技术奖与诺贝尔奖珍惜生命之源从两则消息说起孩子不幸谁之罪? 1 .01 2 .01 3 .01 4 .01 5 .01 6 01 /本刊编辑部“新生代时的北冰洋”等4则/本刊编辑部6 .04(上) 6 .04(下)言论一胎还是二胎了环境保护需要公众参与从《断背山》说同性恋博客为什么这样火?女昏姻的禁忌“食野，，之风何时休? /本刊编辑部1，01(下) /本刊编辑部2.01(下) /本刊编辑部3 .01(下) /本刊编辑部4 .01(下) /本刊编辑部5，01(下) /本刊编辑部6 .01(下)百科聚焦狗年趣谈/郭耕等1.05(上)城市给了我们什么?/胡伟略等2.05(… 相似文献
8.
我的朋友有一辆松花江 63 50面包车 ,他经常请我维修和保养该车。在维修和保养的实践中 ,我发现该车的 2个零部件损坏后拆卸或维修不便 ,遂作了改进。1 方向机的改进方向机运动幅的主动部件为螺旋柱齿轮 ,靠 4 61 0 3球轴承和 94 1 /1 0滚针轴承安装在方向机外壳内 (见图1 )。方向机故障往往是这两个轴承长时期负荷作用下损图 1 改进前方向机局部1—方向机外壳 2—螺旋柱齿轮 3— 46 10 3球轴承4— 941/ 10滚针轴承 5—盲孔坏所致。为确保行车安全 ,轴承一旦损坏 ,必须更换新轴承。拆卸损坏的轴承时 ,因轴承与装配孔为紧配合 ,而装… 相似文献
9.
在CSFB方案部署时,现网中多网络配合给TD-LTE网络维护提出了新的挑战,亟需建设一套CSFB语音业务监测系统来加强LTE网络维护能力。结合我省现网已实现Ao IP的实际情况,本文提出了一种基于A接口仿真的CSFB信令流程监测方法。该方法通过构建BSC仿真模块实现对A over IP接口的仿真,配合移动业务仿真监测系统的e Node B仿真模块,实现CSFB仿真测试对回落到2G网络的支持;结合RNC仿真模块,形成CSFB回落2G/3G网络的全面支撑和实时监测;利用移动业务仿真监测系统的BSC仿真模块、RNC仿真模块、e Node B仿真模块模拟2G/3G/4G多模终端,实现多网络配合下的4G回落过程及多场景下返回4G网络流程的仿真测试。 相似文献
10.
在最佳条件下(TiCl30.15 mol/L NaCl饱和溶液,170℃,4 h,含0添加剂/Ti摩尔比1/10)用水热法在玻璃基板上制备TiO2材料.SEM和XRD技术表征结果说明,生成的TiO2晶体为金红石型.与尿素相比,加酸性含O添加剂不能生成TiO2纳米棒阵列薄膜,但能生成的TiO2微米球或微米花,微米球或花由纳米棒自组装而成.加中性含O添加剂所生成的TiO2材料的形貌最差. 相似文献
11.
通过李群、活动标架,以及调和映射来研究从S2到CPn的共形极小浸入．首先,用一种新方法证明Bolton的一个定理,从S2到的全纯曲线在差一个刚动的情况下由度量唯一决定;其次,利用从 S2到CPn的共形极小浸入来构造从S2到G2,n+1的共形极小浸入;最后,如果φ 是从S2到CPn 的全实共形极小浸入,且φ 是常曲率的,则可以找出具体的等距变换ｇ,使得ｇφ 包含在RPnCPn中． 相似文献
12.
Logarithmic finite-size scaling of the O(n) universality class at the upper critical dimensionality (dc = 4) has a fundamental role in statistical and condensed-matter physics and important applications in various experimental systems. Here, we address this long-standing problem in the context of the n-vector model (n = 1, 2, 3) on periodic four-dimensional hypercubic lattices. We establish an explicit scaling form for the free-energy density, which simultaneously consists of a scaling term for the Gaussian fixed point and another term with multiplicative logarithmic corrections. In particular, we conjecture that the critical two-point correlation g(r, L), with L the linear size, exhibits a two-length behavior: follows governed by the Gaussian fixed point at shorter distances and enters a plateau at larger distances whose height decays as with a logarithmic correction exponent. Using extensive Monte Carlo simulations, we provide complementary evidence for the predictions through the finite-size scaling of observables, including the two-point correlation, the magnetic fluctuations at zero and nonzero Fourier modes and the Binder cumulant. Our work sheds light on the formulation of logarithmic finite-size scaling and has practical applications in experimental systems. 相似文献
13.
Ivan Bradaric Athina P. Petropulu Konstantinos I. Diamantaras 《Journal of The Franklin Institute》2002,339(2):161-187
Higher-order statistics (HOS) are well known for their robustness to additive Gaussian noise and ability to preserve phase. HOS estimates, on the other hand, have been criticized for high complexity and the need for long data in order to maintain small variance. Since rank reduction offers a general principle for reduction of estimator variance and complexity, we consider the problem of designing low-rank estimators for HOS. We propose three methods for choosing the transformation matrix that reduces the mean-square error (MSE) associated with the low-rank HOS estimates. We also demonstrate the advantages of using low-rank third-order moment estimates for blind system estimation. Results indicate that the full rank MSE corresponding to some data length N can be attained by a low-rank estimator corresponding to a length significantly smaller than N. 相似文献
14.
考虑定义在Zd上参数为p的边渗流模型.假设Kn为 [-n,n]d中开簇的个数,研究了关于Kn的鞅中心定理的收敛速度.一般情况下,经鞅中心极限定理的最好收敛速度是O(n-d/2),而我们的结果为Pp((Kn-Ep(Kn))/(Varp(Kn))) ≤x =x∫-∞(1/(2π)) e(-y2)/2dy+o(n-d/2 +ε0)对任意的实数x都成立,这里ε0是区间 0, d/2 上的任意实数.据我们所知,这是关于渗流中心极限定理收敛速度的第一结果.
相似文献
15.
Amer M. Magableh Osamah S. Badarneh Imran Shafique Ansari Taimour Aldalgamouni 《Journal of The Franklin Institute》2018,355(14):6877-6888
Transmit antenna selection with maximal ratio combining at the receiver (TAS/MRC) is a promising technique that can be used to avoid the hardware complexity of multiple input multiple output (MIMO) system without jeopardizing the diversity gain. The generalized Gaussian distribution (GGD) is used to model different kinds of additive noise including Gaussian, Laplacian, uniform, and impulsive. In this paper, we study the bit error performance of TAS/MRC system assuming flat Rayleigh fading channels perturbed by additive white generalized Gaussian noise (AWGGN). To this end, we provide a closed form expression for the average bit error rate of coherent modulation techniques in terms of Mejier’s G function that is readily available in many commercial mathematical software packages like MATLAB and Mathematica. Moreover, we study the asymptotic behavior of the BER at high signal to noise ratio (SNR). Analytical results are verified by simulation. 相似文献
16.
[目的/意义] 在信息检索、科技论文评价和知识结构演化方面,引文分析都起着至关重要的作用。随着格式化全文数据库的出现,引文分析迈入了4.0时代——全文引文分析阶段。但是,目前还没有中文的格式化全文数据库,这极大地制约了全文引文分析在我国科技文献中的研究和应用。[方法/过程] 在本文中我们提出建立高效的中文全文引文分析依赖的数据集和检索平台的方法,主要包括：1）提出了基于规则和SVM分类方法的论文元数据和引用提取方法;2）提出基于Spark平台的实现高效引文内容分析标准化数据集生成方法;3）提出建立引用内容的科技文献检索平台。[结果/结论] 引文内容分析标准化数据集的建立将全面提升全文引文分析在我国科技领域中的研究效能,提高科技文献查找精度。 相似文献
17.
《Journal of The Franklin Institute》2023,360(6):4114-4134
We propose a new approach to apply the chaining technique in conjunction with information-theoretic measures to bound the generalization error of machine learning algorithms. Different from the deterministic chaining approach based on hierarchical partitions of a metric space, previously proposed by Asadi et al., we propose a stochastic chaining approach, which replaces the hierarchical partitions with an abstracted Markovian model borrowed from successive refinement source coding. This approach has three benefits over deterministic chaining: (1) the metric space is not necessarily bounded, (2) facilitation of subsequent analysis to yield more explicit bound, and (3) further opportunity to optimize the bound by removing the geometric rigidity of the partitions. The proposed approach includes the traditional chaining as a special case, and can therefore also utilize any deterministic chaining construction. We illustrate these benefits using the problem of estimating Gaussian mean and that of phase retrieval. For the former, we derive a bound that provides an order-wise improvement over previous results, and for the latter we provide a stochastic chain that allows optimization over the chaining parameter. 相似文献
18.
Shuang Wang Chen-Yu Wang Pengfei Wang Cong Wang Zhu-An Li Chen Pan Yitong Dai Anyuan Gao Chuan Liu Jian Liu Huafeng Yang Xiaowei Liu Bin Cheng Kunji Chen Zhenlin Wang Kenji Watanabe Takashi Taniguchi Shi-Jun Liang Feng Miao 《国家科学评论(英文版)》2021,8(2)
Compared to human vision, conventional machine vision composed of an image sensor and processor suffers from high latency and large power consumption due to physically separated image sensing and processing. A neuromorphic vision system with brain-inspired visual perception provides a promising solution to the problem. Here we propose and demonstrate a prototype neuromorphic vision system by networking a retinomorphic sensor with a memristive crossbar. We fabricate the retinomorphic sensor by using WSe2/h-BN/Al2O3 van der Waals heterostructures with gate-tunable photoresponses, to closely mimic the human retinal capabilities in simultaneously sensing and processing images. We then network the sensor with a large-scale Pt/Ta/HfO2/Ta one-transistor-one-resistor (1T1R) memristive crossbar, which plays a similar role to the visual cortex in the human brain. The realized neuromorphic vision system allows for fast letter recognition and object tracking, indicating the capabilities of image sensing, processing and recognition in the full analog regime. Our work suggests that such a neuromorphic vision system may open up unprecedented opportunities in future visual perception applications. 相似文献
19.
David S. Ross 《Journal of The Franklin Institute》2010,347(7):1281-1308
If a circle in the plane is to roll along a track so that a given point on the circle traces out another circle, what must the shape of the track be? In this paper we give a full answer to this question. This question arises in the design of internal combustion engines and other machines. It is a sort of inverse problem to the classical problem of the trajectories of points on circles rolling inside other circles; the problem whose solution is hypocycloids and hypotrochoids. We derive a system of nonlinear differential equations for the coordinates of the track regarded as a parametric curve. We express the solution of this differential equation in terms of an elliptic integral. We establish the uniqueness of this solution for a given choice of the relevant parameters, the radius of the circle to be traced out and the location on the rolling circle of the tracing point. We show that if we allow the rolling circle to intersect the track, there is at least one track for any circle. We find all possible tracks, and we derive formulas to determine, for a given radius of the circle to be traced out, how many different tracks produce circles of that radius; there is always a finite number, and the number increases roughly linearly with the radius. We characterize those tracks that are mathematical solutions but are not practical physical solutions; tracks that the rolling circle intersects in such a way that it would get stuck. 相似文献