Electromigration-Induced Plastic Deformation in Cu Interconnects: Effects on Current Density Exponent, <Emphasis Type="Italic">n</Emphasis>, and Implications for EM Reliability Assessment

While Black’s equation for electromigration (EM) in interconnects with n = 1 is rigorously based on the principles of electrotransport, n > 1 is more commonly observed empirically. This deviation is usually attributed to Joule heating. An alternative explanation is suggested by the recent discovery of EM plasticity. To examine this possibility, we have retested samples that had been previously subjected to a predamaging phase of high temperature and current densities to determine whether the loss of median time to failure (MTF) is retained. We find that the predamaged samples exhibit MTFs that are permanently reduced, which is a characteristic of EM plasticity.     

Comprehensive evaluation of a CO2‐capturing high‐efficiency power generation system for utilizing waste heat from factories

It is becoming more important to realize CO₂‐capturing power generation systems (PGSs) for drastically decreasing an amount of CO₂ emission into the atmosphere. However, net power generation efficiency (NPGE) of a CO₂‐capturing system has been considered to be greatly deteriorated, since capturing CO₂ requires extra energy. This paper proposes a new CO₂‐capturing PGS that has a high‐efficient NPGE by utilizing waste heat from factories. As an example of a waste heat, exhaust gas with temperature 200°C from refuse incinerator plants is adopted. In the proposed system, the temperature of saturated steam produced by utilizing the waste heat is raised by combusting fuel with the use of pure oxygen in a combustor, and is used as the main working fluid of a gas turbine PGS. It is estimated that the proposed system has a fuel‐to‐electricity NPGE of 59.3%, when turbine inlet temperature (TIT) is assumed to be 1000°C. The economics of the proposed system is also evaluated and the CO₂ reduction cost is estimated to be small; 4.16 U.S. $ t⁻¹ CO₂ compared with 32.1 U.S. $ t⁻¹ CO₂ for a conventional steam turbine PGS. It is shown that CO₂‐capturing is not cost consuming but becomes to be profitable owing to improved power generation characteristics, when its TIT is increased from 1000 to 1200°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Generalized squirming motion of a sphere

A number of swimming microorganisms, such as ciliates (Opalina) and multicellular colonies of flagellates (Volvox), are approximately spherical in shape and swim using beating arrays of cilia or short flagella covering their surfaces. Their physical actuation on the fluid may be mathematically modeled as the generation of surface velocities on a continuous spherical surface—a model known in the literature as squirming, which has been used to address various aspects of the biological physics of locomotion. Previous analyses of squirming assumed axisymmetric fluid motion and hence required all swimming kinematics to take place along a line. In this paper we generalize squirming to three spatial dimensions. We derive analytically the flow field surrounding a spherical squirmer with arbitrary surface motion and use it to derive its three-dimensional translational and rotational swimming kinematics. We then use our results to physically interpret the flow field induced by the swimmer in terms of fundamental flow singularities up to terms decaying spatially as \({\sim } 1/r^3\) . Our results will make it possible to develop new models in biological physics, in particular in the area of hydrodynamic interactions and collective locomotion.     

On the lateral instability of a thin beam under periodic bending loads

The lateral instability of a thin beam under periodic bending loads was investigated. Physical evidences of the instability were observed previously by experiments. But an analytical study has not been reported. The object of this study is to demonstrate the nature and existence of dynamic lateral instability. The harmonic balance method is applied to bifurcation modes which result from the stability change of torsional mode of a beam and then compared with numerical simulations. It is found, in a certain frequency range, that a small bending load results in the lateral instability when damping is small. Inha University     

Evaluation of electromagnetic loads on various design options of the ITER diagnostic upper port plug during plasma disruptions

Electromagnetic (EM) loads due to eddy current and halo current during plasma disruptions are evaluated for the ITER diagnostic upper port plug. To reduce strong EM loads acting on the port plug fixed to the vacuum vessel like a cantilever beam, three design options have been considered: removal of the diagnostic first wall, slitting of the diagnostic shield module and recess of the port plug. The main focus of the present study is to examine the efficacy of these options in terms of EM loads on the upper port plug. It is found that making slits is more effective than removing the first wall. It is also shown that the upper port plug needs to be recessed to reduce the EM load induced by halo current.     

Human discrimination of the rate of motion in the frontal approach of a sound source]

The folic acid antagonists, methotrexate and aminopterin, are known to be teratogenic in humans. The critical period for their teratogenecity is suspected to be between 6 to 8 weeks post-conception. Fetal exposure from 10 to 32 weeks weeks post-conception to methotrexate alone or in combination with other anti-cancer drugs has not resulted in obvious teratogenic effects. Methotrexate is often used to treat cancers but is occasionally used as an abortifacient. The long-term outcome of the fetal aminopterin syndrome has been published in only four adults. We report on a 28-year-old man with fetal methotrexate syndrome and two children with mild manifestations of the syndrome. One child was inadvertently exposed to methotrexate from 7 1/2 through 30 weeks post-conception because his mother was receiving it for treatment of breast cancer. The other was exposed from 11 weeks and 5 days through 25 weeks in an attempt to induce abortion. The 28-year-old man has craniofacial and digital anomalies, growth retardation but normal intelligence as noted in the previously reported cases. These cases remind us of the teratogenicity of methotrexate and should serve as a warning that if methotrexate is used as an abortifaciant and an abortion does not ensue, there is a teratogenic risk.     

Cathode catalyst layer using supported Pt catalyst on ordered mesoporous carbon for direct methanol fuel cell

The development of a cathode catalyst layer based on a supported Pt catalyst using an ordered mesoporous carbon (OMC) for direct methanol fuel cell is reported. An OMC with a mesopore structure between hexagonally arranged carbon nanorods is prepared using a template method. Platinum nanoparticles are supported on the OMC (Pt/OMC) with high metal loading of 60 wt.%. Compositional and morphological variations are made by varying the ionomer content and by compressing the catalyst layer to detect a parameter that determines the power performance. Increase in power density with decrease in the volume fraction of ionomer in the agglomerate comprising the Pt/OMC and the ionomer indicates that mass transport through the ionomer phase governs the kinetics of oxygen reduction. Impedance spectroscopic analysis suggests that a significant mass-transport limitation occurs at high ionomer content and in the compressed cathode. The power density of the optimum cathode layer, which employs a Pt/OMC catalyst with a Pt loading of 2 mg cm⁻², is greater than that of a catalyst layer with 6 mg cm⁻² Pt-black catalyst at a voltage higher than 0.4 V. This would lead to a significant reduction in the cost of the membrane electrode assembly.