9 resultados para 46

em Chinese Academy of Sciences Institutional Repositories Grid Portal


Relevância:

20.00% 20.00%

Publicador:

Resumo:

患儿男,10岁,因"双侧隐睾"就诊.患儿系足月、顺产、5岁时发现头颅大,经医院诊断为脑积水.几岁时做双侧隐睾手术.患儿身高120 cm.头颅发育不规则,颜面不对称,自小严重的智力低下,说话不清.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

本课题是荷兰DSM公司委托研究课题,目的是在保留或基本保留怪尼龙46(PA46)的基本力学性能的情况下,降低PA46的成本,改善其吸水率高、尺寸稳定性差、电性能不好等缺点。有反应挤出法制备了甲基丙烯酸环氧丙酯(GMA)接枝的聚丙烯(PP-g-GMA)。化学滴定和红外光谱(FTIR)证明得到了PP-g-GMA产品。研究了引发剂、单体、反应温度、停留时间和助剂待因素对接枝率、接枝效率、熔体流动速率的影响。以苯乙烯作为助剂,接枝效率可以提高到80%。比较了PP-g-GMA与DSM公司提供的PP-g-GMA的力学性能。PP-g-GMA的抗张强度、杨氏模量、断裂伸长率和冲击强度都高于PP-g-MAH。研究并比较了PP-g-GMA和PP的热学性质。PP-g-GMA结晶度比PP增加,结晶温度提高,PP-g-GMA对Avrami方程有很大的偏差。制备了PA46/PP-g-GMA和PA46/PP共混物并对其力学性能、吸水率、形态结构、动态力学性质、热学性质等进行了研究。与PA46/PP相比,PA46/PP-g-GMA的抗张强度,杨氏模量,弯曲强度和弯曲模量都得到了提高。随着组成的变化,干态下PA46/PP-g-GMA的抗张强度分别比PA46/PP提高10%到35%,杨氏模量提高10%到30%,弯曲强度提高10%-200%,弯曲模量提高10%-50%。PA46/PP-g-GMA的吸水率大大低于PA46/PP,共混物组成为50/50时,PA46/PP的吸水率是PA46/PP-g-GMA的三倍多。扫描电镜(SEM)得到的PA46/PP及PA46/PP-g-GMA的拉伸和冲击断面形态显示,PP-g-GMA在PA46中的粒径尺寸大大变小,变均匀。动态热机械分析(DMA)、示差扫描量热仪(DSC),热失重分析(TGA)结果显示相同组分的PA/PP-g-GMA比PA46/PP的储能模量大,软化温度提高,组分为50/50时,PA46/PP-g-GMA比PA46/PP提高达120 ℃。在PA46/PP-g-GMA和PA46/PP共混体系中,由于两相之间的化学链接,使PP-g-GMA的熔融温度提高1-5 ℃,而PP的熔融温度降低1-7 ℃。相同组分的PA/PP-g-GMA和PA46/PP的热稳定性基本相同。

Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

用1-苯基-3-甲基-4-苯甲酰基-5-吡唑啉酮(PMBP)做萃取剂,氯仿和环己烷为稀释剂,观察了在HCl溶液46Sc的溶剂萃取行为。实验结果表明,从10-3~10-2mol/L的HCl溶液中用PMBP-氯仿(或环己烷)能有效地萃取46Sc,萃取率可达95%以上。另外,对PMBP从HCl溶液中萃取46Sc和234Th的结果也做了比较,结果表明,通过控制水溶液中HCl的浓度,能实现234Th与46Sc的分离。

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich Ar-34 and neutron-rich Ar-46 beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between Ar-34 and Ar-46. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of Ca40-49 isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

用能量密度公式及小液滴模型给出的费米密度分布,并引入中子皮及中子分布弥散度随中子过剩自由度增加而增加这一因素,计算了重离子反应在相互作用势及熔合位垒。熔合位垒的计算值和实验值符合很好,特别是在中重核区域,改善了以前的计算结果。详细研究了亲近势标度,发现用中子皮及中子分布弥散度的变化能较好地解释中子过剩自由度对新近势标度偏离的影响。本工作对奇异核结构与核反应性质的研究无疑是有用的。我们利用HIRFL提供的46.7MeV/u ~(12)C束轰击~(58)Ni、~(115)In、~(197)Au研究了反应中发射的α粒子角分布和能谱。从速度表象中洛仑兹不变截面等高图中明显看到发射α粒子的三个源。用这三个源的运动模型成功拟合了α粒子能谱,所提取的参数符合费米气体模型计算结果,并讨论了能谱及拟合参数对靶的依赖关系。认为快速源实质上来自弹核碎裂或类弹核碎裂

Relevância:

20.00% 20.00%

Publicador:

Resumo:

本文分析了翁牛特旗46年(1957-2002年)逐月降水量和平均气温。结果表明:气温呈非连续增暖趋势,其中年平均气温线性变化率为0.39℃.(10a)-1,年平均最高气温线性变化率为0.19℃.(10a)-1,年平均最低气温线性变化率为0.93℃.(10a)-1;最低气温上升速率是最高气温的1-4倍,气温日较差显著减小。上世纪60年代较50年代有所增暖,80年代后期开始明显升温,90年代是近50年来最暖的10年。1987年开始转暖,其后呈连续性增暖趋势,1998年为1957年以来的最暖年,年平均气温7.7℃,高于1957年2.9℃。降水以平均5-7年的周期变化,并从50年代到90年代呈连续性递减趋势,线性变化率为-11.7mm.(10a)-1,90年代较50年代年降水减少了39.4mm。

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Isothermal and nonisothermal crystallization kinetics of nylon-46 were investigated with differential scanning calorimetry. The equilibrium melting enthalpy and the equilibrium melting temperature of nylon-46 were determined to be 155.58 J/g and 307.10 degreesC, respectively. The isothermal crystallization process was described by the Avrami equation. The lateral surface free energy and the end surface free energy of nylon-46 were calculated to be 8.28 and 138.54 erg/cm(2), respectively. The work of chain folding was determined to be 7.12 kcal/mol. The activation energies were determined to be 568.25 and 337.80 kJ/mol for isothermal and nonisothermal crystallization, respectively. A convenient method was applied to describe the nonisothermal crystallization kinetics of nylon-46 by a combination of the Avrami and Ozawa equations.