过渡层厚度对Be/CuCrZr热等静压连接性能影响

在铍上用物理气相沉积(PVD)镀上10μmTi 和10μmCu,再添加不同厚度的(分别为0.00mm、0.25mm、 0.50mm、0.75mm、1.00mm)无氧铜作为中间过渡层,与CuCrZr/316L(N)复合板基座铜合金侧通过热等静压连接。采用光学显微镜、扫描电镜(SEM)与电子探针(EPMA)、X 射线衍射仪(XRD)、剪切试验等方法确定了界面组织与性能。试验结果表明：各厚度无氧铜模块连接成功,界面无裂纹、空洞等缺陷,钛铜间出现三层明显的反应层,分别为CuTi₂、CuTi 以及Cu₄Ti。添加无氧铜厚度越大,剪切强度越大。     

双侧下颌支矢状劈开截骨术后患者可施加合适咬合力的数值研究

双侧下颌支矢状劈开截骨术在临床手术中广泛用于治疗缩颌、凸颌和颌面不对称患者的颌面畸形症状。本文用数值方法研究双侧下颌支矢状劈开截骨术并前移下颌骨后患者可施加的合适咬合力。首先,用缩颌患者的CT断层扫面数据建立下颌骨、关节盘、关节窝和相关软组织的高度几何相似性的几何模型;然后,用有限元模型模拟双侧下颌支矢状劈开截骨术后患者的咬合过程。通过分析发现,术后关节盘上的位移处于正常的范围,而应力却远远超过正常范围,因此,将应力因素作为确定术后患者可施加的合适咬合力的标准。当施加正常咬合力的25%时,关节盘上的应力分布和术前没有显著性差异,同时下颌骨上的应力水平也处于正常范围。     

质子数Z 分别位于Ru 之上和之下的A~(100~126) 丰中子原子核三轴形变在原子核形状变迁和共存中的重要作用(英文)

基于Ru (Z = 44) 丰中子同位素中存在最大三轴形变的理论预言和实验证据,综述了近年来Rh (Z = 45),Pd (Z =46), Ag (Z =47), Cd (Z =48)(质子数Z 位于Ru,Z =44 之上)及Zr (Z =40), Nb (Z =41), Mo (Z =42),Tc (Z =43)(质子数Z 位于Ru,Z =44 之下) 的A~ (100~126) 丰中子同位素中关于三轴形变的形状变迁和形状共存系统性研究的重要进展。252Cf 自发裂变瞬发 射线-- 三重符合、特别是新建立的--- 四重符合数据的系统观测和研究,在Ru, Pd, Cd 和Nb 丰中子同位素中显著扩展或首次观测到了一系列能带,为这个核区原子核形状的研究提供了新的、重要的实验数据。联系此前报道的有关进展,使用PES, TRS, PSM, CCCSM 和SCTAC 理论模型计算拟合新的实验数据,在该核区沿同中素和同位素链,并随自旋和激发能变化各自由度,跟踪原子核形状渐进变化,获得了新的系统性研究成果,显著扩展和深化了人们对原子核形状变迁和形状共存的认知。对于Ru 及其上的Rh (Z = 45), Pd (Z = 46), Ag (Z = 47) 和Cd (Z = 48) 丰中子同位素的研究表明:Rh 丰中子核具有比最大值稍小的三轴形变,γ = 28°,并在103{106Rh 同位素链上鉴别出了手征对称破缺;在三轴形变核112Ru和114Pd(N = 68)中发现了三轴原子核的摆动运动,该摆动运动也可能在114Ru (N = 70)中存在;观察到了从具有最大三轴形变的110,112Ru 中手征破缺到稍小三轴形变的112,114,116Pd 中扰动的手征破缺的过渡;在较软的Ag 核中观察到了丰富的谱学结构,在104,105Ag 中鉴别出了可能的手征对称破缺,在较重的115,117Ag 中提出了趋于三轴形变的软度;具有小形变的Cd核的能级结构被解释为准粒子耦合、准转动和软三轴形变;最近的库伦激发的研究提供了Z = 50, N = 82满壳附近122,124,126Cd 核中出现核集体性的实验和理论证据;上述研究成果展现出从Ru中的最大三轴形变(γ=30°,三轴形变极小增益为0.67 MeV), 经具有大三轴形变的Rh核γ=28°),到Pd核中的稍小、但稳定于中等自旋到高自旋区的三轴形变(γ~41°,三轴形变极小增益为0.32 MeV),再经Ag核中的软度,最后到具有很小形变、但仍出现集体性质、包括软三轴形变的Cd核的过渡。对于Pd核转动带交叉系统性的研究揭示了其第一带交叉(νh_11/2)2 中子转动顺排的上行驱动,和第二带交叉(πg_9/2)2质子转动顺排的下行驱动效应,成功地解释了114Pd 中的三轴摆动运动,并给出了110-118Pd同位素链中理论早已预言、而比早期理论预言更为完整准确的形状渐进变迁和形状共存的图像。根据该核区的系统研究,发现最大三轴形变出现在112Ru,而在相邻的偶Z(Pd)同位素链,三轴形变极小的中心在114Pd, 两者均为N = 68。上述系统性研究沿相邻的Ru和Pd偶Z同位素链,在N =68同中素中鉴别出最大三轴形变,均比理论预言的108Ru 和110Pd 多4个中子。在Z值位于Ru (Z = 44) 之下的Zr (Z = 40), Nb (Z = 41), Mo (Z = 42) and Tc (Z = 43) 丰中子同位素中,Y和Zr核具有很强的轴对称四极形变,而在较重的Zr同位素中出现了自由度;较重的Nb核(A = 104~106) 基态具有中等程度的软三轴形变和强四极形变,随着自旋和激发能的增加,过渡到接近于轴对称的强四极形变;而较轻的Nb核(A≤103) 基态均接近轴对称形状;在Nb同位素链上基态由球形到强四极形变的形状突变发生在100Nb(N = 59),在100-106Nb同位素链中基态的软三轴形变随中子数增加而增加;在Nb核中还观察到关于软三轴形变的形状共存;Mo核具有大的三轴形变,观察到了振动和手征对称破缺;Tc核具有比最大值稍小的三轴形变,γ=26°,并观察到了手征对称破缺。质子数Z从41到48的A~(100~126)丰中子同位素,特别是Pd和Nb 同位素,呈现出关于三轴形变的过渡特征。This paper reviews the systematic investigations and understanding for the shape transitions and coexistence with regard to triaxial deformations in A s 100 to 126 neutron-rich Rh (Z = 45), Pd (Z = 46), Ag (Z = 47), Cd (Z = 48) and Zr (Z = 40), Nb (Z = 41), Mo (Z = 42), Tc (Z = 43) isotopes with Z beyond and below Ru (Z = 44), respectively, in Ru the maximal triaxial deformation having been predicted and deduced. The recent measurements and studies of prompt triple- and four-fold, γ-γ-γ and γ-γ-γ-γ, coincidence data from the spontaneous fission of 252Cf using Gammasphere have yielded considerable expansion and extension or first observation of the bands in Ru, Pd, Cd, and Nb isotopes,which provided important data for the studies of nuclear shapes in this region. Combined with previous investigations, recent systematic studies of the new data well reproduced by PES, TRS, PSM, CCCSM and SCTAC model calculations have traced shape changes along the isotonic and isotopic chains, respectively,and with changing excitations/spins as well, significantly expanding our knowledge of shape transitions/coexistence in nuclei.For the neutron-rich Ru and beyond, Rh, Pd, Ag and Cd isotopes, triaxial deformations γ= 28°,slightly smaller than the maximal value, were deduced in Rh (Z = 45) isotopes, with chiral symmetry breaking proposed in 103-106Rh; onset of wobbling motions were identified in 112Ru and 114Pd (N =68),and probably also in 114Ru (N =70); evolution from chiral symmetry breaking in 110,112Ru with maximal triaxial deformations to disturbed chirality in 112,114,116Pd with less pronounced triaxial deformations was proposed; rich nuclear structure was proposed in soft Ag isotopes with possible chiral doubling structure suggested in 104,105Ag, and softness towards triaxial deformation proposed in heavier 115,117Ag;quasi-particle couplings, quasi-rotations and soft triaxiality were suggested in Cd (Z =48) isotopes with small deformations; onset of collectivity was recently suggested in 122,124,126Cd in the vicinity of Z =50 and N = 82 closed shells by studies of Coulomb excitations; shape evolutions from maximal triaxial deformations in Ru (γ=30°, with triaxial minimum energy gain of 0.67 MeV), through Rh with large triaxial deformations ( γ=28°), to less pronounced triaxiality in Pd (with triaxial minimum energy gain of 0.32 MeV), then soft triaxiality in Ag, and finally to slightly deformed Cd isotopes but with emergence of collectivity and soft triaxiality were proposed. The systematic studies of the band crossings in Pd revealed up-rising drivings of the first band crossings caused by (νh_11/2)2 and down-sloping drivings of the second band crossings by (πg_9/2)2, explained the onset of wobbling motions in 114Pd,and showed a long-sought picture of shape evolution and coexistence in the Pd isotopic chain which is more complete but complex than earlier predictions. Based on the systematic studies in the mass region,maximal triaxial deformation is found to be reached in 112Ru and less-pronounced triaxiality centered at 114Pd, both for N =68, four neutrons more than predicted in earlier theoretical calculations.In the neutron-rich Zr (Z =40), Nb (Z =41), Mo (Z =42) and Tc (Z =43) isotopes with Z just below Ru, large quadrupole deformations of axially symmetric shapes were deduced in Y and Zr isotopes, with emergence of the degree of freedom having been suggested for heavier Zr isotopes; medium triaxial deformations were deduced for the ground states of heavier (A > 104) Nb isotopes, and, with increasing excitations and spins, evolution from medium triaxial deformations with strong quadrupole deformations at ground states to nearly axially-symmetric shapes were deduced; light Nb isotopes (A6103) have near axially-symmetric shapes with strong quadrupole deformations; combining with the identification of onset of strong quadrupole deformation at 100Nb in the Nb isotopic chain, an increase of soft triaxiality with increasing neutron number was proposed in 100-106Nb. Shape coexistence with regard to soft triaxiality is also proposed in Nb isotopes; large triaxial deformations, vibrations and chiral doublets were proposed in Mo isotopes; chiral doubling and large triaxial deformations (γ ~26°) slightly smaller than the maximal triaxiality were suggested in Tc isotopes.The neutron-rich nuclei with Z ranging from 41 through 48 and A ~100 to 126, especially the Pd and Nb isotopes are thus found to be transitional nuclei with regard to triaxiality.     

电光双稳态系统的混沌控制与同步

根据长延时状态下电光双稳系统的特点,提出了实现其混沌控制与同步的具体方案.数值模拟的结果表明：适当选取驱动强度及驱动系统的状态,不仅可以实现对响应系统不同周期状态的稳定控制,还可以实现驱动系统与响应系统间的广义混沌同步.以最大李雅普诺夫指数为标准,给出了实现混沌同步的参数范围.     

ICP-AES法测定枸橼酸铋制剂中的杂质元素

采用微波消解的方法溶样,用ICP-AES法同时测定了枸橼酸铋制剂中的Ca、Mg、Cr、Mn等杂质元素的含量,考察了微波消解的条件和基体元素Bi对被测元素分析谱线强度的影响。方法的检出限为0．6～16ng／mL,相对标准偏差为1．58％～6．64％,加标回收率为92％～104％。该方法简单、快速、准确,结果令人满意。     

开放实验室教学模式的实践与思考

山东大学化学与化工学院开放实验室自2003年5月份开始向二、三年级本科生进行全天候开放。由本科生自主组成课题组,经院专家组筛选后进入开放实验室。目前这种教学模式已经纳入正常教学工作,对学生的培养已经产生和正在产生着较大的影响。     

可中断的多任务平行机排序问题

Leung等(Preemptive multiprocessor order scheduling to minimize total weighted flowtime [J]. European Journal of Operational Research, 2008, 190: 40-51)研究了如下问题: 有 n 个订单, 其中每个订单 i 含有 n_i 个不同的工件. 所有的订单在零时刻已经到达, 并且工件的加工是可中断的. 每个订单 i有一个权重 \omega_i, 定义订单 i 的完工时间 C_i 为订单 i 最后一个完工工件的完工时间. 目标是找到一个可行排序使得加权总完工时间\sum\limits_{i=1}^n \omega_iC_i 最小. Leung等证明了这个问题是NP-难的, 给出了一个近似算法, 并且分析了该算法的最坏情况界. 但是定理2的证明存在一些错误. 证明了尽管定理2的证明过程存在错误, 但是其结论仍然正确. 另外, 对上述模型的一种特殊情形给出了更好的近似算法.     

表面张力对Rayleigh-Taylor不稳定性谐波的影响

Using the method of the parameter expansion up to the third order, explicitly investigates surface tension effect on harmonics at weakly nonlinear stage in Rayleigh-Taylor instability (RTI) for arbitrary Atwood numbers and compares the results with those of classical RTI within the framework of the third-order weakly nonlinear theory. It is found that surface tension strongly reduces the linear growth rate of time, resulting in mild growth of the amplitude of the fundamental mode, and changes amplitudes of the second and third harmonics, as is expressed as a tension factor coupling in amplitudes of the harmonics. On the one hand, surface tension can either decrease or increase the space amplitude; on the other hand, surface tension can also change their phases for some conditions which are explicitly determined.     

傅里叶光谱仪高精度光谱定标研究

为了提高傅里叶光谱仪光谱定标精度,减小光谱定标误差,基于风云四号大气垂直探测仪实验室气体池光谱定标数据,进行傅里叶光谱仪高精度光谱定标算法研究。首先,分析了傅里叶光谱仪的分光原理,并在对参考激光波数漂移、光线离轴、以及有限视场引起光谱波数偏移的原理进行分析后,得出傅里叶光谱仪光谱定标公式及定标参数的计算方法;接着分析了快速傅里叶变换(FFT)的栅栏效应和干涉图截断产生的sinc函数造成的光谱定标误差较大的原因;然后通过对比几种不同的光谱细化方法,选择高效的快速Chirp Z-transform(CZT)进行光谱细化,解决FFT光谱分辨率较低导致光谱误差较大的问题;通过对气体池参考气体在HITRAN数据库中的理论谱线,用Gaussian线型展宽并卷积sinc函数处理后作为光谱定标参考谱线的方式,减小由sinc函数引起的谱线间串扰造成的光谱定标误差,从而提高光谱定标精度。最后,使用实验测得的数据对该光谱定标算法进行验证,对比使用CZT细化光谱前后定标误差,和参考谱线处理前后的定标误差,证明该算法可以有效提高光谱定标精度,最高可将光谱定标误差减小10倍以上。     

ZL114A铝合金本构关系与失效准则参数的确定

针对航空发动机机匣材料ZL114A铝合金,构建描述该材料在较大温度范围下大变形及失效行为的材料模型。通过万能试验机及分离式霍普金森压杆试验装置测试ZL114A铝合金在常温准静态、高温和高应变率下的力学性能,分析温度和应变率对材料流动应力的影响。采用有限元程序和优化算法反求25～375℃内材料的硬化参数,结合高应变率(1 310～5 964 s^-1)下材料的动态行为关系,构建包含塑性应变、温度及应变率的经验型本构模型。开展缺口拉伸、缺口压缩等试验并建立相对应的有限元模型,获取材料在不同应力三轴度下的失效应变,标定分段形式的Johnson-Cook (J-C)失效准则参数。通过不同温度下的平板侵彻试验和数值模拟验证失效准则及其参数的有效性。结果表明,ZL114A铝合金具有明显的应变硬化、温度软化及高应变率强化特性;具有应力饱和特征的Hockett-Sherby (HS)硬化模型较为准确地描述材料大变形下的力学行为;构建的材料本构关系可以描述ZL114A铝合金在大应变、宽温度、高应变率下的力学行为;分段形式的失效准则具有预测不同温度下材料失效行为的能力。