Thermal Conductance for Single Wall Carbon Nanotubes

We report a theoretical analysis of the phonon thermal conductance, \kappa (T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100K, \kappa (T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length is slightly varied, \kappa (T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior of \kappa (T).Comment: Revtex, 4 figure

Electronic band gaps and transport in aperiodic graphene superlattices of Thue-Morse sequence

We have studied the electronic properties in aperiodic graphene superlattices of Thue-Morse sequence. Although the structure is aperiodic, an unusual Dirac point (DP) does exist and its location is exactly at the position of the zero-averaged wave number (zero-$\bar{k})$. Furthermore, the zero-$\bar{k}$ gap associated with the DP is robust against the lattice constants and the incident angles, and multi-DPs can appear under the suitable conditions. A resultant controllability of electron transport in Thue-Morse sequence is predicted, which may facilitate the development of many graphene-based electronics.Comment: Accepted for publication in Applied Physics Letters; 4 pagese, 5 figure

Electronic band gaps and transport properties in periodically alternating mono- and bi-layer graphene superlattices

We investigate the electronic band structure and transport properties of periodically alternating mono- and bi-layer graphene superlattices (MBLG SLs). In such MBLG SLs, there exists a zero-averaged wave vector (zero-$\overline{k}$) gap that is insensitive to the lattice constant. This zero-$\overline{k}$ gap can be controlled by changing both the ratio of the potential widths and the interlayer coupling coefficient of the bilayer graphene. We also show that there exist extra Dirac points; the conditions for these extra Dirac points are presented analytically. Lastly, we demonstrate that the electronic transport properties and the energy gap of the first two bands in MBLG SLs are tunable through adjustment of the interlayer coupling and the width ratio of the periodic mono- and bi-layer graphene.Comment: More discussion is added and the English is polished. Accepted for publication in EP

End effect of corroded steel bar in concrete specimen during corrosion test by galvanostatic method

The galvanostatic method is a commonly used accelerated corrosion method in studying the durability of concrete structures caused by steel corrosion. If this method is not adequately controlled, the ends of steel bars will be corroded seriously (this phenomenon is called end effect), which is not common in natural corrosion. How to effectively control the end effect during electrified corrosion is helpful to make the characteristics of electrified corrosion more similar to that of natural corrosion. In this paper, experimental and electromagnetic numerical simulation methods are used to study the influence of cathode and corrosion medium coverage area along the longitudinal direction on the end effect of steel bar before producing corrosion crack. The results showed that the wider the coverage area of the corrosive medium (NaCl solution with a mass concentration of 3%), the longer the corrosion area of reinforcement along the longitudinal direction, the more prone the end effect is. The change of cathode length has no noticeable effect on the corrosion area of reinforcement along the longitudinal direction when the corrosion medium coverage area is constant. Increasing the distance between the end of the corrosion medium coverage area and the end of the reinforcement can effectively avoid the end effect

General Dynamics of Topology and Traffic on Weighted Technological Networks

For most technical networks, the interplay of dynamics, traffic and topology is assumed crucial to their evolution. In this paper, we propose a traffic-driven evolution model of weighted technological networks. By introducing a general strength-coupling mechanism under which the traffic and topology mutually interact, the model gives power-law distributions of degree, weight and strength, as confirmed in many real networks. Particularly, depending on a parameter W that controls the total weight growth of the system, the nontrivial clustering coefficient C, degree assortativity coefficient r and degree-strength correlation are all in consistence with empirical evidences.Comment: 4 pages, 4 figure

End effect of corroded steel bar in concrete specimen during corrosion test by galvanostatic method

Corrosion of steel bars is the main durability problem of concrete structures, which seriously endangers the safety and service life of reinforced concrete (RC) structures. When studying such problems, the electrifying corrosion method is often used to obtain corroded components. How to effectively control the corrosion area of steel bars is the key to improve the applicability of the corrosion method. In this paper, experimental and electromagnetic numerical simulation methods are used to study the influence of cathode and corrosion medium coverage area along the longitudinal direction on the corrosion area of steel bar before concrete protective layer corrosion cracking. The results show that the numerical simulation method based on electromagnetism can be used to predict the corrosion area of reinforcement before concrete corrosion cracking. When the resistivity of corrosive medium is much lower than that of concrete, the wider the coverage area, the longer the corrosion area of reinforcement along longitudinal direction, the more prone the end effect is, and the change of cathode length has no obvious effect on the corrosion area of reinforcement along longitudinal direction when the corrosion medium coverage area is constant. Increasing the distance between the end of the corrosion medium coverage area and the end of the reinforcement can effectively avoid the end effect