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91.
从解剖结构和神经生理功能的角度提出了一种神经元模型,讨论了标准神经元的符号、人工神经元网络和通用数字计算机的联接方式。列举了几种典型的人工神经元网络的例子。 相似文献
92.
一种基于熵算子的边界检测方法 总被引:1,自引:0,他引:1
报道作者在进行三维医学图象处理中对边界检测算法的最新研究成果,提出一种新的边界检测熵算子,并首次给出快速有效地确定算法中阈值的自适应方法,这种亲折边界检测算法运行速度快,同时又能较好地提取物体轮廓,最后文中以2幅二维图象进行了试验,说明该算法具有实用性和有效性。 相似文献
93.
历史上洞庭湖面积的变迁 总被引:5,自引:0,他引:5
卞鸿翔 《湖南师范大学自然科学学报》1986,(2)
本文根据历史资料,对所谓“洞庭湖方八百里”的说法进行了分析,并论证了各个历史时期的湖水面积的变动。作者估算:汉晋南朝时期的湖面积约为6,000平方公里,唐宋时期缩小为3,300平方公里,元明时期扩大到5,600平方公里左右,清代中期,缩小为不足4,000平方公里,清末又扩大达5,400平方公里,二十世纪上半叶基本变动于4,000至5,000平方公里之间。湖面积这种周期性变化的原因就在于:湖底淤垫与湖泊水位抬升之间关系的演化,以及围湖垦殖活动的兴衰。 相似文献
94.
以大秦线为中心,从系统角度出发,采用网络分析的方法,考虑到“八五”、“九五”运输发展需要,综合论述了北通路各条线路的战略分工,使北通路各条线路能充分利用.同时,对现存的大秦线装、运、卸各环节的问题提出改进的建议. 相似文献
95.
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97.
HaiTao Zong XinYu Zhang LiXin Li LinYan Bian ShunXing Liang ChunLin Tan 《科学通报(英文版)》2012,57(11):1219-1222
The thermal stability and glass forming ability (GFA) of Zr35-xTi30Cu7.5Be27.5Agx (x = 0-10) alloys were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and ultrasonic techniques. We found that the addition of 1 at.% Ag can considerably enhance the GFA as indicated by an increase in the critical glass dimension from 15 mm in the Zr35Ti30Cu7.5Be27.5 alloy to 20 mm in the Zr34Ti30Cu7.5Be27.5Ag1 alloy. However, with the addition of more Ag the supercooled liquid region (△Tx) and y parameter (defined as Tx/(Tg+Tl)) drastically decreased from 155 K and 0.436 to 76 K and 0.363, respectively, resulting in a decrease in the GFA. Additionally, the elastic constant (the ratio of shear modulus to bulk modulus or Poisson’s ratio) was also used as a gauge to evaluate the GFA in Zr35-xTi30Cu7.5Be27.5Agx alloys. 相似文献
98.
The amorphous Fe78Si9B13 alloy was used as a heterogeneous Fenton catalyst in the process of phenol degradation.The influences of main operating parameters such as reaction temperature,catalyst amount,hydrogen peroxide dosage and initial pH of solution on phenol degradation rate were investigated.The maximum mineralization of phenol was achieved at 60°C,6 g/L Fe78Si9B13, 0.31 mol/L hydrogen peroxide,with an initial pH of 2.5.More than 99%of phenol was completely removed under the optimum conditions within 10 min for a solution containing 1000 mg/L of phenol.Batch experiments for solutions containing phenol con- centrations ranging from 50 to 2000 mg/L were investigated under the above conditions and the same excellent degradation rate was obtained.The Fe78Si9B13 showed better catalytic activity than iron powder and Fe 2+ .Addition of n-butannol(hydroxyl radical scavenger)decreased the degradation rate of phenol,which demonstrates that hydroxyl radicals were mainly responsible for the removal of phenol.We demonstrated that phenol may be degraded by hydroxyl radicals decomposed by hydrogen peroxide on the surface of Fe78Si9B13 and illustrated the reaction mechanism for this process.This amorphous alloy exhibited high stability in recycling experiments and showed excellent reuse performance even after continuous operations of 8 cycles. 相似文献
99.
An in vitro feasibility study of the use of poly(ethylene carbonate) (PEC) as a
biodegradable coating material for drug-eluting stents is reported, and the performance of PEC
is compared with that of poly(lactic-co-glycolic acid) (PLGA). Scanning electron microscopy
(SEM) images of PEC and PLGA discs after treatment with an alkaline KO2 solution as a
superoxide source showed that the PEC maintained its integrity whereas holes and small particles
appeared during the treatment of PLGA. Sirolimus and paclitaxel were loaded into PEC and
PLGA in order to study drug release performance. Attenuated total reflectance–infrared (ATR–
FTIR) spectroscopy of sirolimus, PEC and the sirolimus-loaded PEC coating showed that no
chemical reaction occurred between sirolimus and PEC. The results of atomic force microscopy
(AFM) revealed that the mean roughness (Ra) values of the bare metal stent (BMS) and the drugeluting
stent (DES) were 2.3 nm and 1.0 nm, respectively. After balloon expansion experiments, no
delamination or destruction of the PEC coating was observed. The drug release profile of sirolimus
was different from that of paclitaxel when PEC was employed as the drug carrier, and the release curves of sirolimus were different when PEC and PLGA were used as drug carriers. All the
experimental results demonstrated that PEC was one of the best potential stent-coating materials. 相似文献
100.
以12根抗拔桩承载力为研究对象,利用4参数的贝塔分布拟合出抗拔桩承载力试计比(承载力实测值和计算值的比)的概率分布.通过K-S检验法检验指出:贝塔分布的拟合精度优于常见的正态分布、对数正态分布和极值I型分布.利用蒙特卡罗法计算出抗拔桩承载力的可靠度指标,计算结果表明:承载力试计比的均值、荷载组合、荷载比和安全系数对可靠度有显著的影响.最后利用荷载抗力系数设计法给出了抗拔桩的抗力系数. 相似文献