We observed a negative differential resistance (NDR) along with single-electron tunneling (SET) in the electron transport of electromigrated break junctions with metal-free tetraphenylporphyrin (H2BSTBPP) at a temperature of 11 K. The NDR strongly depended on the applied gate voltages, and appeared only in the electron tunneling region of the Coulomb diamond. We could explain the mechanism of this new type of electron transport by a model assuming a molecular Coulomb island and local density of states of the source and the drain electrodes. 相似文献
We have compared catalytic activity of Co and Fe in a growth process of single-walled carbon nanotube (SWNT) by chemical vapor deposition using ethanol as a carbon source and SiO2 as a catalyst-supporting material. Changes of the catalyst precursors (Co- and Fe acetate) in the growth process were carefully observed at three different stages: (i) after oxidation in air at 400 °C but before heating to the growth temperature (800 °C), (ii) after heating to the growth temperature in flowing Ar and H2 but before starting the nanotube growth and (iii) after the growth process is over. During the growth of SWNT, the Co catalyst took the form of β-Co, resulting in a high yield growth. On the contrary, the Fe catalyst formed a silicate, Fe2SiO4, showing a poor catalytic ability. Our result shows that chemical reactions between the catalyst precursors and their supporting materials sensitively affect the catalytic ability. 相似文献
The reconstitution technique by surface-activated joining (SAJ) has been investigated for the reuse of undeformed portions of tested Charpy impact specimens. SAJ can be achieved by the removal of surface contamination by rotating one of the specimens in a vacuum while applying modest frictional force.
In this study, the temperature distribution during joining and hardness distribution after joining were measured. Charpy impact tests were then performed to evaluate the thermal and mechanical effects on Charpy specimens reconstituted by SAJ. The results showed that SAJ can be achieved with a hardened width of less than 1·5 mm, and on a width of less than 3 mm heating up above reactor operation temperatures, produced in either side of the joined interface. Charpy transition temperatures could be evaluated from the reconstituted Charpy specimens. It is concluded from comparison with other welding methods that the SAJ method is most suited for reconstituting irradiated surveillance specimens. 相似文献
This paper presents reconsideration of value creation in production from various aspects of value viewpoints in several disciplines such as production engineering, social sciences, and human sciences. The focal point of investigations is value co-creation by the provision of products and services in and for society. In the past, some methods of social sciences and others proved to be useful in making production more efficient. At present, such methods must help to realise value creation. In fact, production must become more effective in response to human needs in social, economic, and environmental dimensions. Along with the theoretical apparatus, this paper presents some case studies indicating the importance of value creation in production, followed by future perspectives of value co-creation in production. 相似文献
An interactive animation method for viscoelastic materials builds on Rouse's spring-bead model. Particles are connected one-dimensionally by spring forces to represent single polymer chains. The method approximates the collision's force between particles through the particle density's gradient. This model lets the viscoelasticity be changed dynamically by severing the interconnection of polymer chains. 相似文献
Growth rate has a direct impact on the productivity of nitride LED production. Atmospheric pressure growth of GaN with a growth rate as high as 10 μm/h and also Al0.1Ga0.9N growth of 1 μm/h by using 4 inch by 11 production scale MOVPE are described. XRD of (002) and (102) direction was 200 arcsec and 250 arcsec, respectively. Impact of the growth rate on productivity is discussed. 相似文献
ABSTRACT A deep-penetration shielding experiment was performed at the CERN High-energy AcceleRator Mixed-field (CHARM) facility. The protons (24 GeV/c) were injected into a 50-cm-thick copper target and the released neutrons were transmitted through a bulk concrete shield located vertically upward from the target, where they were measured with bismuth and aluminum activation detectors placed at various penetration distances in the shield. From the radionuclide production rate in the activation detectors, the attenuation profiles through the concrete shield were obtained for the reactions of 209Bi(n,xn)210-xBi(x = 4–9) and 27Al(n,α)24Na. The attenuation length of the high-energy neutrons through ordinary concrete was estimated as 120 g/cm2, in good agreement with Monte Carlo simulations using simple slabs as a universal geometry implemented in Particle and Heavy Ion Transport System (PHITS) code. Proton energy dependence of attenuation length was also investigated with simulations by PHITS code and comparisons with the published data were discussed. 相似文献