Constructing codes identifying sets of vertices

For all t ≥ 2, we give an explicit construction of an infinite family of graphs such that G admits a code identifying sets of at most t vertices of G of cardinality O(t ² ln |V(G)|) for all members G of the family. This beats the best previously known explicit construction by a factor of t ².      

Electron correlation effects in the presence of non-symmetry dictated nodes

We numerically study the effect of non-symmetry dictated nodes (NSDN) on electron correlation effects for spinless electrons. We find that repulsive interaction between electrons can enhance the overlap between nearest neighbors in the tight binding Hamiltonian, in the presence of NSDN. Normally, in the absence of NSDN, attractive interaction between electrons give such an effect and repulsive interaction gives the opposite effect.     

Experimental and Theoretical Investigation of Surface Electrization in a Combustion Product Flow

The electrization of cooled and non-cooled surfaces in a combustion product flow loaded with charged soot particles is investigated experimentally and theoretically. The charging currents of the inner surface of a cylinder located in a combustion (propane in air) product flow with a relatively high soot content and the charging currents of cooled and non-cooled cylinders located in a combustion product jet with a relatively low soot content are determined. Physico-mathematical models are constructed for the new effects observed experimentally and these models are theoretically and numerically analyzed.     

A time-domain homogenization technique for lamination stacks in dual finite element formulations

A time-domain homogenization technique is developed to take the eddy currents in lamination stacks into account with dual 3-D magnetodynamic b$\mathbf{b}$- and h$\mathbf{h}$-conform finite element formulations. The lamination stack is considered as a source region carrying predefined current density and magnetic flux density distributions describing the eddy currents and skin effect in each lamination. These distributions are related and are approximated with sub-basis functions. The stacked laminations are then converted into continuums with which terms are associated for considering the eddy current loops produced by parallel fluxes, through the homogenization of the sub-basis function contributions.     

Fuel cell cathode with Nafion and platinum: Calculating its overall performance with consideration of gas-and vapor-exchange processes in the gas-diffusion layer

The overall performance of cathodes with solid polymer electrolytes is calculated for three different cases in which gas-and vapor-exchange processes in the gas-diffusion layer are considered. First of all, specific results are presented for calculating the overall performance of oxygen and air cathodes under the assumption that external diffusion restrictions are completely absent. Then with these same conditions (i.e., all the parameters characterizing the active layer of the cathode remain the same), results of the overall performance are given for the idealized case in which gas exchange in the gas-diffusion layer causes the appearance of limiting currents, but in this case vapor exchange is completely ignored. Finally, an analysis is carried out to determine how vapor-exchange processes in the gas-diffusion layer alter overall cathode performance and what measures should be taken to reduce the significance of external diffusion restrictions.     

Theory of porous electrodes: Calculation of overall cathode characteristics for the case where the polarization curve has segments with different slopes

It is demonstrated how one should carry on with calculations of overall currents and other parameters that characterize active layers of porous electrodes in the case where polarization curves for the catalyst display two or more segments with different slopes and exchange currents. A calculation of overall currents presumes that the active layer of an electrode has an optimum thickness, over which the current reaches a maximum. The entire range of values of the cathode potential is considered, specifically, the high potentials (from a steady-state potential up to the point where there is observed an inflection in the polarization curve), the intermediate potentials (near the front surface and near the rear surface of the active layer there are realized segments of the polarization curve with different slopes), and the low potentials (throughout the entire thickness of the active layer there is observed a second segment of the polarization curve). To give an example, calculations of overall characteristics of a cathode with Nafion and platinum are performed.     

自旋极化的电流——2007年度诺贝尔物理学奖评述

2007年诺贝尔物理学奖授予法国物理学家阿尔贝·费尔(Albert Fert)和德国物理学家彼得·格伦贝格（Peter Grünberg）,以表彰他们发现了巨磁电阻（giant magnetoresistance, GMR）效应.这是在铁磁和非磁薄膜交替组成的人工超晶格中观察到的.GMR现象起源于载流子自旋与材料磁性的相互作用.该效应的应用革新了硬盘中读取数据的技术,使硬盘技术在过去十年得到飞速发展;另一方面,GMR效应的发现是新的自旋电子学的开端.通过电子自旋的量子效应,人们可以期待更多的发现和创新技术.     

分布式电流刺激抑制心肌组织中螺旋波

利用两种恒定电信号刺激介质不同区域来产生分布式电流, 外界分布式电流内化为跨膜电流后在介质中形成稳定的梯度力可抑制螺旋波的传播. 当螺旋波被消除后系统进一步演化为均匀态且对应的膜片电位采样序列逐渐趋于一个稳定值. 在考虑噪声情况下, 该方法仍然能消除螺旋波, 对其采样序列分析也验证了方法的可靠性.关键词：螺旋波分布式电流激发介质