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111.
On the basis of the electromagnetic field mode matching theory, the coupling efficiency ratio from spatial light to Bragg fiber is analyzed, which shows that the coupling efficiency ratio is related to the radius of focused facular, the core radius of Bragg fiber and wave number of the core. By optimizing the value of such parameters appropriately, the Bragg fiber coupling efficiency ratio can be improved. It is also important for the analysis of the coupling efficiency of Bragg fiber, which can be applied to the free optical communication system and laser radar system. 相似文献
112.
本文证明了若群G旗传递地作用于4-(v,k,2)设计,且G是仿射型群,则SL(ad,pa)G0,这里v=pd,a|d,0是p元域上的d维向量空间的零向量。 相似文献
113.
Xiaohang Liu Liangping Zhou Weijun Peng Chaofu Wang He Wang 《Magnetic resonance imaging》2013,31(8):1318-1324
PurposeTo investigate biexponential apparent diffusion parameters of prostate central gland (CG) cancer, stromal hyperplasia (SH), and glandular hyperplasia (GH) and compare with monoexponential apparent diffusion coefficient (ADC) value for discriminating prostate cancer from benign hyperplasia.Materials and MethodsTwenty-one CG cancer foci, 23 SH and 26 GH nodules in the CG were analyzed in 39 patients (19 with CG cancer, 20 with peripheral zone cancer but no CG cancer) who underwent preoperative conventional DWI (b-value 0, 1000 s/mm2) and a 10 b-value (range 0 to 3000 s/mm2) DWI. All of the cancer and hyperplastic foci on MR images were localized on the basis of histopathologic correlation. The ADC value of the monoexponential DWI, and the fast apparent diffusion coefficient (ADCf), slow apparent diffusion coefficient (ADCs) value and the fraction of ADCf (f) of the biexponential DWI were calculated for all of the lesions. Receiver operating characteristic (ROC) analysis was performed for the differentiation of CG cancer from SH and GH.ResultsThe ADC values (× 10? 3 mm2/s) were 0.87 ± 0.11, 1.06 ± 0.15, and 1.61 ± 0.27 in CG cancer, SH and GH foci, respectively, and differed significantly, yielding areas under the ROC curve (AUCs) of 1.00 and 0.80 for the differentiation of carcinoma from GH and SH, respectively. The ADCf (× 10? 3 mm2/s), ADCs (× 10? 3 mm2/s) and f for cancer were 1.92 ± 0.38, 0.53 ± 0.17, and 47.7 ± 6.1%, respectively, which were lower than the same values for GH (3.43 ± 0.65, 1.12 ± 0.21, 61.1 ± 8.7%) (all p < 0.01). The ADCf and ADCs for cancer were also lower than those for SH (3.11 ± 0.30, 0.79 ± 0.21) (all p < 0.01). The ADCf yielded AUCs (1.00, p > 0.01) that were comparable to those from ADC for the differentiation of cancer from GH, while ADCf yielded higher AUCs (0.92) compared with ADC (p < 0.01) for the differentiation of cancer from SH. ADCs and f revealed AUCs of 0.97 and 0.90, respectively, for the differentiation of cancer from GH, and the ADCs offered relatively lower AUCs (0.68) for differentiating cancer from SH.ConclusionBiexponential DWI could potentially improve the differentiation of prostate cancer in CG, and the ADCf of the biexponential model offers better accuracy than ADC. 相似文献
114.
In this article, without computing exact gradient and Jacobian, we proposed a derivative-free Polak-Ribière-Polyak (PRP) method for solving nonlinear equations whose Jacobian is symmetric. This method is a generalization of the classical PRP method for unconstrained optimization problems. By utilizing the symmetric structure of the system sufficiently, we prove global convergence of the proposed method with some backtracking type line search under suitable assumptions. Moreover, we extend the proposed method to nonsmooth equations by adopting the smoothing technique. We also report some numerical results to show its efficiency. 相似文献
115.
116.
We propose a conception – coupled caloric effect where the enhanced caloric effects originate from the coupling among magnetic, ferroelectric, and structural degrees of freedom. Specifically, as the magneto-electric case, the magnitude of the coupled caloric effect was evaluated for a ferromagnetic–ferroelectric system using a phenomenological calculation based on Landau phase transition theory. The isothermal entropy change is greatly enhanced by increasing the magneto-electric coupling strength. This work indicates that the caloric effect in a ferromagnetic–ferroelectric coupled system consists of pure magnetic entropy change (ΔSM), pure ferroelectric one (ΔSE), and coupled one (ΔSME) that plays a significant part. The counterpart of the last one in magneto-structural coupled system was usually neglected. Our study provides a route to energy-efficient refrigeration via realization of coupling among various ferroic orders. 相似文献
117.
Kaikai Wang Jimei Zhou Yuting Jiang Miaomiao Zhang Chao Wang Dong Xue Weijun Tang Huamin Sun Jianliang Xiao Chaoqun Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6446-6450
The first manganese‐catalyzed oxidation of organosilanes to silanols with H2O2 under neutral reaction conditions has been accomplished. A variety of organosilanes with alkyl, aryl, alknyl, and heterocyclic substituents were tolerated, as well as sterically hindered organosilanes. The oxidation appears to proceed by a concerted process involving a manganese hydroperoxide species. Featuring mild reaction conditions, fast oxidation, and no waste byproducts, the protocol allows a low‐cost, eco‐benign synthesis of both silanols and silanediols. 相似文献
118.
红外光谱法动态跟踪聚羟基脂肪酸酯(PHAs)的热变性过程 总被引:2,自引:0,他引:2
本文利用FTIR光谱法研究了常温下和升温、降温过程中PHB,P(HO-co-HD)及不同组分的P(HB-co-HV)和P(HB-co-HH)共聚物的变化。结果表明,PHB、P(HB-co-HV)和P(HB-co-HH)在变温过程中红外光谱图发生了明显变化,此过程是物理变化,且过程可逆。 相似文献
119.
上证指数收益率分布的拟合 总被引:3,自引:0,他引:3
本文旨在讨论上证指数收益率序列的分布特征 ,通过对上证指数 1 997年 5月 2 3日至 2 0 0 1年 7月1 3日 ,总计 1 0 0 0多个交易日的统计分析 ,发现上证指数收益率的分布具有“尖峰、厚尾”的特性 .我们试图用文献 [1 ]给出 Lévy flight来拟合其分布 ,但结果并不理想 .为此我们提出了一种类似 Weibull分布的函数来拟合上证指数收益率分布 ,模拟结果较好 .同时 ,我们按通常的方法对尾部作了截尾处理 ,以更接近实际数据在尾部表现出来的“厚尾”现象 相似文献
120.
Aixiang Huang Weijun Zhou Anran Wang Minfeng Chen Qinghua Tian Jizhang Chen 《Journal of Energy Chemistry》2021,(3):475-481
Thanks to low cost,high safety,and large energy density,aqueous zinc-ion batteries have attracted tremendous interest worldwide.However,it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production.Herein,we use a molten salt method to synthesize nanostructured manganese oxides.The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture.It is found that the α-MnO2/Mn2O3 nanocomposite with the largest mass ratio of Mn2O3 delivers the best electrochemical performances among all the products.And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder.In this situation,the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g-1 at 0.2 and 3 Ag-1,respectively.After 1000 cycles,it can retain 86.2% of the capacity at the 2 nd cycle.Thus,this nanocomposite holds great promise for practical applications. 相似文献