Effect of Cerium on the Properties of CuPNiSn Amorphous Alloys

CuPNiSn amorphous alloys are good brazing materials at medium temperature for replacement of silver bearing brazing materials.The crystallization temperature,wettability,tensile strength of Cu-Cu joints and the microstructure of joints for three compositional series are reported.Some rare earth elements were added in two series.It has been found that grains are refined and the tensile strengths increase as in- creasing rare earth content.The results also show that the brittle fracture turns to plastic one for the joints with reducing amount of(Ni+Sn),and the tensile strength is increased.

Research on Oil/Gas In-pipe Inspection Robot

A new type of in-pipe mobile robot was designed and developed on the basis of w heel in-pipe robot and crawler in-pipe robot. The three sets of driving wheels circumferentially 120° apart in the cross section, both front and rear driving wheels are distributed on the same parallelogram mechanis m. The driving motor drives the three sets of driving wheels by worm couple, the regulating motor makes the three sets of driving wheels push against the pipe inwall with stable and adequate pressing force by the ball screw pair and p ressure sensor, so the in-pipe robot can provide adequate and stable traction force. The robot mechanism is simple and sm all in size and work reliably . It is particularly suitable to the pipe with diameter 400～650 mm.

机械分割的小鼠桑椹胚和囊胚的发育能力

利用机械方法二等份分割小鼠的桑椹胚、早期囊胚和晚期囊胚,并在体外培养分割的半胚到晚期囊胚。将这些囊胚移植到假孕受体鼠子宫内以评价他们附植后发育的能力。在体外培养中发现,囊胚期分割的胚胎比桑椹胚期分割的胚胎有较高的成活率。通过附植前胚胎细胞数量分析得知,囊胚期半胚的细胞数量大约是对照组的一半,但内细胞团细胞与整个胚胎细胞的数量比不变。虽然从半胚发育到囊胚期的胚胎附植率仅略低于对照组,但半胚形成胎儿的能力却显著低于全胚。组织学分析表明,附植后的这种低成活率现象是由于缺乏卵柱发育造成的,而此卵柱则与半胚中的内细胞团的细胞数量减少有关。移植到第3天假孕受体鼠中的半胚,附植后的发育情况明显地比移植到第4天受体中的好。

MECHANISM OF PATHOLOGICAL CHANGES OF INTRAVENTRICULAR HEMORRHAGE IN DOGS

Objective To probe the mechanism of pathological changes of intraventricular hemorrhage(IVH). Methods The evaluation of neurological status,serial CT scans and pathological examination were applied on the canine model of IVH. The ventricular volume and blood clot volume were measured based on the CT images. Results The normal adult canine ventricle tend to be slitlike. After injection, the ventricle was obviously dilated by the blood clot. The linear regression of ventricular volume against blood clot volume was significant in the first week. From then on, however, while the clots continued to shrink, the ventricular volume showed progressive enlargement. The clots were lysed completely within 3 to 4 weeks. The linear regression of the degree of ventricular dilatation against the first clot volume was also significant. In the pathological examination, we found the ependymal lining of ventricular system was destroyed and neurons in the subependymal areas developed acidophil necrosis, which was prominent around Sylvian aqueduct. Conclusion Hemorrhagic ventricular dilatation(HVD) is a prominent feature of IVH and also is a strong indicator for poor prognosis. Ischemic changes of periventricular neurons in some important structures may be the most direct cause for poor outcome of IVH. It may be induced by periventricular vascular structures compressed by HVD, increased intracranial pressure, cerebral vasospasm and others.

Theoretical Analysis of the Fluctuation Theorem Applied to Electric Circuits

We carry out a theoretical analysis of the fluctuations in the Johnson–Nyquist noise in an RC electric circuit being driven by a non-ideal constant current source. Using the appropriate Langevin equation, we derive the fluctuation theorem for the system. This analysis exhibits some interesting features. Firstly, the average of the dissipation function is not necessarily just an instantaneous entropy production, i.e. the work being done on the circuit by the external power source divided by the ambient temperature. Secondly, by appropriate selection of the values for the circuit components,the transient response of the system can be made identical to the nonequilibrium steady state response. In the limit of an ideal current source, the average of the dissipation function reduces to the entropy production. Our analysis accurately reproduces published experimental results.

Topological and dynamical phase transitions in the Su–Schrieffer–Heeger model with quasiperiodic and long-range hoppings

Disorders and long-range hoppings can induce exotic phenomena in condensed matter and artificial systems.We study the topological and dynamical properties of the quasiperiodic SuSchrier-Heeger model with long-range hoppings.It is found that the interplay of quasiperiodic disorder and long-range hopping can induce topological Anderson insulator phases with nonzero winding numbers ω=1,2,and the phase boundaries can be consistently revealed by the divergence of zero-energy mode localization length.We also investigate the nonequilibrium dynamics by ramping the long-range hopping along two different paths.The critical exponents extracted from the dynamical behavior agree with the Kibble-Zurek mechanic prediction for the path with W=0.90.In particular,the dynamical exponent of the path crossing the multicritical point is numerical obtained as 1/6~0.167,which agrees with the unconventional finding in the previously studied XY spin model.Besides,we discuss the anomalous and non-universal scaling of the defect density dynamics of topological edge states in this disordered system under open boundary condictions.