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排序方式: 共有422条查询结果,搜索用时 15 毫秒
1.
针对目前大多数人脸识别算法参数多、计算量大,难以部署到移动端和嵌入式设备中的问题,提出了一种基于改进MobileFaceNet的人脸识别方法。通过对MobileFaceNet模型结构的调整,将bottleneck模块优化为sandglass模块,改良深度卷积和逐点卷积的相对位置,适当增大sandglass模块的输出通道数,从而减少特征压缩时的信息丢失,增强人脸空间特征的提取。实验结果表明:改进后的方法在LFW测试数据集上准确率达99.15%,模型大小和计算量分别仅为原算法的61%和45%,验证了所提方法的有效性。 相似文献
2.
Gordon H. Dash Jr. Nina Kajiji 《International Transactions in Operational Research》2014,21(6):899-918
A dynamic portfolio policy is one that periodically rebalances an optimally diversified portfolio to account for time‐varying correlations. In order to sustain target‐level Sharpe performance ratios between rebalancing points, the efficient portfolio must be hedged with an optimal number of contingent claim contracts. This research presents a mixed‐integer nonlinear goal program (MINLGP) that is directed to solve the hierarchical multiple goal portfolio optimization model when the decision maker is faced with a binary hedging decision between portfolio rebalance periods. The MINLGP applied to this problem is formed by extending the separable programming foundation of a lexicographic nonlinear goal program (NLGP) to include branch‐and‐bound constraints. We establish the economic efficiency of applying this normative approach to dynamic portfolio rebalancing by comparing the risk‐adjusted performance measures of a hedged optimal portfolio to those of a naively diversified portfolio. We find that a hedged equally weighted small portfolio and a hedged efficiently diversified small portfolio perform similarly when comparing risk‐adjusted return metrics. However, when percentile risk measures are used to measure performance, the hedged optimally diversified portfolio clearly produces less expected catastrophic loss than does its nonhedged and naively diversified counterpart. 相似文献
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Lei Lu Qingli Hao Wu Lei Xifeng Xia Peng Liu Dongping Sun Xin Wang Xujie Yang 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(43):5833-5843
Catalysts with low‐cost, high activity and stability toward oxygen reduction reaction (ORR) are extremely desirable, but its development still remains a great challenge. Here, a novel magnetically separable hybrid of multimetal oxide, cobalt ferrite (CoFe2O4), anchored on nitrogen‐doped reduced graphene oxide (CoFe2O4/NG) is prepared via a facile solvothermal method followed by calcination at 500 °C. The structure of CoFe2O4/NG and the interaction of both components are analyzed by several techniques. The possible formation of Co/Fe N interaction in the CoFe2O4/NG catalyst is found. As a result, the well‐combination of CoFe2O4 nanoparticles with NG and its improved crystallinity lead to a synergistic and efficient catalyst with high performance to ORR through a four‐electron‐transfer process in alkaline medium. The CoFe2O4/NG exhibits particularly comparable catalytic activity as commercial Pt/C catalyst, and superior stability against methanol oxidation and CO poisoning. Meanwhile, it has been proved that both nitrogen doping and the spinel structure of CoFe2O4 can have a significant contribution to the catalytic activity by contrast experiments. Multimetal oxide hybrid demonstrates better catalysis to ORR than a single metal oxide hybrid. All results make the low‐cost and magnetically separable CoFe2O4/NG a promising alternative for costly platinum‐based ORR catalyst in fuel cells and metal‐air batteries. 相似文献
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《国际计算机数学杂志》2012,89(3-4):191-206
This paper deals with the efficient implementation of implicit methods for solving stiff ODEs, in the case of Jacobians with separable sets of eigenvalues. For solving the linear systems required we propose a method which is particularly suitable when the large eigenvalues of the Jacobian matrix are few and well separated from the small ones. It is based on a combination of an initial iterative procedure, which reduces the components of the vector error along to the nondominant directions of J and a projection Krylov method which reduces the components of the vector error along to the directions corresponding to the large eigenvalues. The technique solves accurately and cheaply the linear systems in the Newton's method, and computes the number of stiff eigenvalues of J when this information is not explicitly available. Numerical results are given as well as comparisons with the LSODE code. 相似文献
6.
Fangyue Chen Wenhui Tang Guanrong Chen 《International Journal of Circuit Theory and Applications》2009,37(3):433-451
This paper presents a single‐layer perceptron (SLP) scheme with an impulse activation function (IAF) and a dynamic neuron (DN) with a trapezoidal activation function (TAF). Combining with some interesting properties of the offset levels, it is shown that many linearly non‐separable Boolean functions can be realized by using only one SLPwIAF or one DNwTAF. In the present work, a few appropriate IAF and TAF are adopted, and the inverse offset level method is used for the design of the SLPwIAF synaptic weights and the DNwTAF templates. The XOR and NXOR Boolean operations with two inputs and all 152 non‐separable Boolean functions with three inputs can be easily implemented by one SLPwIAF or one DNwTAF. Finally, the entire set of 152 DNwTAF templates associated with 152 non‐separable Boolean functions of three inputs is completely listed. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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In this paper a straightforward z-domain procedure for realizing multidimensional transfer functions with either numerator or denominator polynomial separable is presented. This procedure yields structures with minimum number of multipliers. It is shown that the number of delay elements can be reduced by selecting the optimum values for certain parameters. To facilitate this theorems that are applicable for some special cases are presented. 相似文献
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采用溶胶-凝胶法分别在离子液体1-丁基-3-甲基咪唑四氟硼酸盐[BMim]BF4、1-丁基-吡啶四氟硼酸盐[BPy]BF4和1-丁基-3-甲基咪唑醋酸盐[BMim]Ac的辅助下制备可磁分离TiO2/CoFe2O4(TCF)光催化材料, 采用X射线衍射分析(XRD)、N2吸附-脱附分析(BET)和透射电子显微镜(TEM)研究了离子液体结构对可磁分离TiO2的结构和性能的影响。结果显示: 200 ℃焙烧后样品[BMim]BF4-TCF和[BPy]BF4-TCF有锐钛矿相TiO2 生成, 而样品[BMim]Ac-TCF和TCF只有经400 ℃焙烧才出现锐钛矿相的衍射峰。当焙烧温度为800 ℃时, 样品[BMim]BF4-TCF主要以锐钛矿相TiO2存在(相对含量为92.6%), 说明离子液体中含有[BF4-]基团能降低锐钛矿相的晶化温度和能提高锐钛矿相高温稳定性。400 ℃焙烧后[BMim]BF4-TCF和[BPy]BF4-TCF的比表面积分别为125.7和120.3 m2/g, 高于[BMim]Ac-TCF(77.8 m2/g)和不加离子液体所制备样品TCF(63.7 m2/g)。说明阴离子BF4-有利于形成较大比表面积的TiO2。在模拟太阳光照射120 min后, 经400 ℃焙烧后的样品[BMim]BF4-TCF、[BPy]BF4-TCF、[BMim]Ac- TCF对亚甲基蓝的降解速率分别为96%、87%、64%。 相似文献
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