泡沫铝／铸铁层合结构高速移动工作台的性能分析

为研究泡沫铝／铸铁层合结构材料作为高速机床移动工作台的可行性和优越性,设计了该新型结构的机床工作台。采用ANSYS软件对其静态性能、动态性能进行研究,计算其质量和惯性力。结果表明,与传统材料铸铁工作台相比,该新型结构材料机床工作台静态性能与其相当,而其动态性能得到较大的提高,质量和惯性力有很大降低。证明了泡沫铝／铸铁层合结构材料在高速和超高速移动工作台中应用的可行性。     

泡沫铝／环氧树脂复合材料压缩力学行为的仿真分析

根据所制备的开孔泡沫铝／环氧树脂复舍材料的结构特点,对其材料结构进行了合理的简化。在此基础上采用ANSYS／KS—DYNA软件对该材料的压缩力学行为进行有限元仿真分析;得出了该材料在压缩过程中的变形和失效过程以及应力-应变关系随其结构参数（泡沫铝孔径、泡沫铝相等密度）及应变率的变化规律。如上规律与已有文献的物理实验研究结果相一致,从而证明了该仿真方法的合理可行性,为泡沫铝孔洞填充复合材料的性能研究提供了一种新方法。     

新型泡沫铝层合结构溜槽的结构设计及降噪性能研究

为了降低煤矿溜槽工作时的振动噪声,探索溜槽降噪的新途径,将泡沫铝层合结构用于制造矿用溜槽。针对溜槽工作的特点,设计泡沫铝层合结构矿用溜槽的新结构,使其结构满足原型结构溜槽的刚度要求,并且质量小于原型结构溜槽。运用声学软件Virtual.Lab对两种槽体在不同激振频率下的声场进行声学边界元分析。结果表明,泡沫铝层合结构溜槽可以降低对环境的辐射噪声,在低频段、中频段还是高频段都优于现有的溜槽结构,其平均声压级可减小5~6 d B左右,从而提高溜槽的环保性。     

泡沫铝汽车碰撞吸能器仿真分析

提出了在汽车保险杠和前纵梁之间安装泡沫铝吸能器的方案,并对此结构进行了总体设计.采用 CATIA ANSYS DYNA3D联合建模求解技术对汽车碰撞进行了仿真分析,得出了安装泡沫铝吸能器前后汽车质心加速度曲线、吸能曲线及车体应力分布图.结果表明,应用泡沫铝汽车碰撞缓冲吸能器可提高汽车的安全性.本研究为泡沫铝在汽车中的应用提供了参考依据,也为汽车满足轻质、节能、环保、安全等方面的需要提供了新途径     

制备泡沫铝的一种新方法:烧结溶解法

烧结溶解法是近几年发展起来的一种制造泡沫铝的新工艺，具有可以精确控制孔洞形状，尺寸和孔隙率及其分布等特点，具有较好的质量价格综合指数，是生产均匀或梯度微细开孔中密度泡沫铝的有效方法，所制泡沫铝在吸能，吸音等领域有广泛的应用前景。本文简要介绍烧结溶解法的原理与工艺，所制泡沫铝的组织特征与机械性能，并讨论与其它各类现有方法相比所具有的优势与局限。     

磁流体-泡沫金属减振器磁路优化设计

利用ANSYS软件对磁流体-泡沫金属减振器的磁路进行数值模拟研究,对影响其性能的磁路级数及相邻两级线圈中电流流向的异同进行了分析.研究结果表明,相同条件下采用多级磁路较单级磁路具有较多的优点,并且多级磁路中相邻激励线圈绕向相反能够更好的改善磁路性能.本研究为磁流体-泡沫金属减振器的设计提供依据.     

超低介电常数材料和多孔SiOCH薄膜

集成电路的特征尺寸将降低到0．1μm，这时器件内部金属连线的电阻和绝缘介质层的电容所形成的阻容造成的延时、串扰、功耗已经成为限制器件性能的主要因素。目前集成电路的金属连线价质层材料为铝／二氧化硅配置，用电阻更小的铜取代铝作金属连线，用低介电常数(低K)材料取代二氧化硅作介质层成为科学意义重要、应用价值巨大的研究课题，微电子器件正经历着一场材料的重大变革中。本文着重评述了纳米尺度微电子器件对低介电常数(低k)薄膜材料的要求，介绍了多孔硅基低k薄膜的研究进展。     

金属基复合材料界面层阻尼功能研究

采用CVD技术制备了具有不同界面层的C-f/Al金属基复合材料，获得了一种界面层阻尼功能设计的新方法. 研究发现具有特殊界面层的C-f/Al复合材料的抗拉强度、弹性模量和阻尼性能比无界面层时都有明显增加，并且不同界面层的效果不同. 碳层对复合材料阻尼性能的提高效果最大，硅层的提高效果不如碳层，碳硅混合层的效果居中. 涂层的厚度也影响了阻尼提高的效果，较厚的碳层效果更好，这是由于提高了复合材料的阻尼应变振幅效应而产生的. 研究认为发生在界面层的微滑移是其主要的阻尼机制.     

铝诱导结晶法制备高度(111)择优取向多晶硅薄膜及成核分析

采用铝诱导结晶法在玻璃衬底上制备了具有高度(111)择优取向的多晶硅薄膜.首先通过磁控溅射在玻璃衬底上先后沉积铝层和非晶硅层,然后在480℃下退火1h以完成铝诱导结晶.退火后硅层与铝层发生置换,形成了具有高度(111)择优取向以及良好结晶质量的多晶硅层.通过对Al2O3氧化膜结构变化及晶格匹配进行分析,阐明了铝诱导结晶过程中(111)择优取向的铝层间接促使多晶硅(111)择优取向成核的作用机制.     

添加羰基铁粉的聚氨酯泡沫特征参数辨识及低频吸声性能研究

探究羰基铁粉添加和聚醚多元醇与异氰酸酯不同比例对聚氨酯泡沫的物理特征参数和低频吸声性能的影响,旨在改善传统聚氨酯泡沫的低频吸声效果.首先基于JCA(Johnson-Champoux-Allard)模型,采用最小二乘法估算磁性聚氨酯泡沫的物理特征参数(流阻率、孔隙率、曲折率、黏性特征长度、热性特征长度),同时基于传递函数法,利用双通道阻抗管,测量聚氨酯/磁性聚氨酯泡沫在64~1600 Hz的吸声性能.结果表明,相同比例聚醚多元醇与异氰酸酯的聚氨酯/磁性聚氨酯泡沫,羰基铁粉的加入会明显改变聚氨酯泡沫的特征参数,其中流阻率和孔隙率均增加,增加范围分别为82.9%~211.3%和0.8%~5.3%,曲折率降低范围为32.7%~74.5%,黏性特征长度降低范围为81.4%~94.0%,但热性特征长度无明显变化.同时在64~500 Hz范围内的低频吸声性能均显著改善,特别是聚醚多元醇与异氰酸酯比例为100:60时,因加入羰基铁粉,使得磁性聚氨酯泡沫与聚氨酯泡沫相比,其低频吸声性能能够提高64%.该新型智能磁性聚氨酯泡沫有望通过调整特征参数来满足不同频段吸声的功能需求,可对智能吸声降噪器件的优化设计提供一定的参考价值.     

Soziale Verhaltensweisen bei hörenden und gehörlosen Dompfaffen (Pyrrhula pyrrhula L.)

Summary The behaviour of bullfinches (Pyrrhula) after removal of the cochlea is studied. The influence of acoustical and optical stimuli upon the social contacts is compared. Parts of the social behaviour are controlled mainly acoustically, e.g. the attraction of a single bird by a calling fellow. Also the final raising of young birds is not possible without acoustical contacts between parents and offspring. The formation of pairs, however, nest-building, laying of fertilized eggs, and breeding are performed normally by birds without hearing. Also the social order within a group of bullfinches regulates itself without acoustical perception by its members. The alarming behaviour seems to be transferred within a group by optical signals.     

Stimulus anticipation in following rhythmic acoustical patterns by tapping

Subjects followed rhythmic acoustical sequences by finger-tapping. Tapping onset preceded stimulus onset by a value close to 30 ms. It is suggested that this temporal difference might correspond to one cycle of a hypothetical timing mechanism in the brain which has been observed with other experimental paradigms.     

Stimulus anticipation in following rhythmic acoustical patterns by tapping

Summary Subjects followed rhythmic acoustical sequences by finger-tapping. Tapping onset preceded stimulus onset by a value close to 30 ms. It is suggested that this temporal difference might correspond to one cycle of a hypothetical timing mechanism in the brain which has been observed with other experimental paradigms.This work was supported by DFG, Po 121/13.     

Influence of reactive oxygen species production by monoamine oxidase activity on aluminum-induced mitochondrial permeability transition

Treatment of Ca2+-loaded mitochondria with both aluminum and tyramine results in a swelling of higher amplitude than with aluminum alone, while tyramine alone is ineffective. The phenomenon is accompanied by H2O2 production and thiol and pyridine nucleotide oxidation. Cyclosporin A, N-ethylmaleimide or dithioerythritol completely prevent these effects, while catalase exhibits a lower inhibition, pointing to the induction of the permeability transition (MPT) by an oxidative stress. Reactive oxygen species are generated by the interaction of aluminum with the inner membrane and the oxidation of tyramine by monoamine oxidase on the outer membrane. This different localization determines the oxidation of critical thiol groups located on both internal and external sides of pore-forming structures, resulting in MPT induction. The reduced effect by aluminum or the inefficacy by tyramine, when implied alone, can be attributable to the oxidation of thiol groups located only on the internal or external side, respectively. Ultrastructural observations show that aluminum plus tyramine induce the typical configuration of mitochondria that have undergone the MPT. Instead, with aluminum alone, the sensitive subpopulation, although swollen, preserves the outer membrane and shows an apparently orthodox configuration.     

Obtaining copulation solicitation displays in female canaries without estradiol implants

Female domesticated canaries (Serinus canaria) respond to conspecific song with copulation solicitation display (CSD) between 22 and 27 days after their first offspring has hatched. This period could be used to investigate the acoustical preferences of female canaries. This non-invasive method respects the natural reproductive cycle and could be an alternative to the invasive method of estradiol implants.     

聚氨酯改性混凝土材料探讨

已有研究表明与普通水泥砂浆相比,采用相同水灰比的聚氨酯水泥砂浆可以获得较好的耐久性。本文把聚氨酯作为混凝土改性材料,经初步研究发现,掺入聚氨酯的混凝土坍落度损失增大,向混凝土中加入聚羧酸减水剂解决了这一问题。本文通过试验以抗压强度为指标初步优化了聚氨酯改性混凝土的养护条件和加料顺序。此外,加入到混凝土中的匀泡剂由于对聚氨酯有极优异的乳化能力,有可能形成了极细的泡孔和狭窄的孔径分布以及极高的闭孔率,可以提高聚氨酯混凝土的耐久性。本文选择了不同厂家提供的甲、乙两种匀泡剂并进行强度试验,以抗压强度为指标选择强度较高一种的应用于聚氨酯改性混凝土。     

Depth perception by means of ambient sounds in a small mammal

Summary Golden hamsters placed on a jumping stand from which they can descend onto a shallow or deep landing platform prefer to descend on to the shallow platform, even when tested under IR-light without tactile cues. This preference disappears for subjects with plugged ears. The simultaneous recording of the animal's behaviour and possible emission of ultrasound as well as experiments in which the external acoustical conditions or the sound-reflecting properties of the jumping apparatus were altered suggest that the animals use certain parameters of the ambient sound field for depth perception. Acknowledgments. This research was supported by the Fonds National Suisse de la Recherche Scientifique, grant No. 3.349.74.     

Inactivation of human glutamate dehydrogenase by aluminum

Aluminum inactivated glutamate dehydrogenase (GDH) by a pseudo-first-order reaction at micromolar concentrations. A double-reciprocal plot gave a straight line with a k_inact of 2.7 min^-1 and indicated the presence of a binding step prior to inactivation. The inactivation was strictly pH dependent and a marked increase in sensitivity to aluminum was observed as the pH decreased. At a pH higher than 8.5, no inactivation was observed. The completely inactivated GDH contained 2 mol of aluminum per mole of enzyme subunit monomer. When preincubated with enzyme, several chelators such as citrate, NaF, N-(2-hydroxyethyl) ethylenediaminetriacetic acid or ethylenediaminetriacetic acid efficiently protected the enzyme against the aluminum inactivation. In a related experiment, only citrate and NaF released the aluminum from the completely inactivated aluminum-enzyme complex and fully recovered the enzyme activity. Ferritin, NADP⁺, or nerve growth factor did not show any effects on the recovery of the aluminum-inactivated GDH activity. The dissociation constant for the aluminum-enzyme complex was calculated to be 5.3 M. Although aluminum has been known to form a complex with nucleotides, no such effects were observed in the inactivation of GDH by aluminum as determined using GDHs mutated at the ADP-binding site, NAD⁺-binding site or GTP-binding site. Circular dichroism studies showed that the binding of aluminum to the enzyme induced a decrease in helices and sheets and an increase in random coil. Therefore, inactivation of GDH by aluminum is suggested to be due to the conformational change induced by aluminum binding. These results suggest a possibility that aluminum-induced alterations in enzymes of the glutamate system may be one of the causes of aluminum-induced neurotoxicity.Received 25 July 2003; received after revision 27 August 2003; accepted 15 September 2003