Ac-cotunneling through an interacting quantum dot under a magnetic field

We analyze inelastic cotunneling through an interacting quantum dot subject to an ambient magnetic field in the weak tunneling regime under a non-adiabatic time-dependent bias-voltage. Our results clearly exhibit photon-assisted satellites and an overall suppression of differential conductance with increasing driving amplitude, which is consistent with experiments. We also predict a zero-anomaly in differential conductance under an appropriate driving frequency.Comment: Phys. Lett. A (in press

Unconventional magnetic phase diagram of cuprate superconductor La2-xSrxCuO4 at quantum critical point x = 1/9

We propose a new magnetic phase diagram of La2-xSrxCuO4 around a quantum critical point x = 1/9 based on field-cooled magnetization measurements and critical fittings. A new phase boundary Tm2(H) is discovered which buries deeply below the first order vortex melting line in the vortex solid phase. The coupling between superconductivity and antiferromagnetism is found to be attractive below Tm2(H) while repulsive above. The attractive coupling between superconducting order and static antiferromagnetic order provides compelling experimental evidence that the antiferromagnetism microscopically coexists and collaborates with the high temperature superconductivity in cuprates.Comment: 17 pages, 4 figure

Research on Rapidly Shaped Charge Cutting Technology of Aircraft Damaged Thin-Wall Structure

Shaped charge cutting technology has been introduced into the field of aircraft structure repair to rapidly reshape irregular holes in thin-walled structures. In the present research, numerical calculation of the dynamic cutting process by ANSYS and experiments of shaped charge cutting on a 2A12 aluminum alloy plate with 2 mm thickness have been carried out. It was found that fast kerf is smooth, producing a neat edge and good linearity. The incision fracture section is arranged in neat rows on a corrugated strip, and the lines are clear. Otherwise, the lower part is slightly messy without obvious distribution rules. The target plate separation method of cumulative cutting is a kind of “pre-penetration” and “late tear” method. The application of shaped charge cutting technology can aid in repair of aircrafts’ thin-walled structural damage

Frictional drag between non-equilibrium charged gases

The frictional drag force between separated but coupled two-dimensional electron gases of different temperatures is studied using the non-equilibrium Green function method based on the separation of center-of-mass and relative dynamics of electrons. As the mechanisms of producing the frictional force we include the direct Coulomb interaction, the interaction mediated via virtual and real TA and LA phonons, optic phonons, plasmons, and TA and LA phonon-electron collective modes. We found that, when the distance between the two electron gases is large, and at intermediate temperature where plasmons and collective modes play the most important role in the frictional drag, the possibility of having a temperature difference between two subsystems modifies greatly the transresistivity.Comment: 8figure

First long-term study of particle number size distributions and new particle formation events of regional aerosol in the North China Plain

Atmospheric particle number size distributions (size range 0.003–10 μm) were measured between March 2008 and August 2009 at Shangdianzi (SDZ), a rural research station in the North China Plain. These measurements were made in an attempt to better characterize the tropospheric background aerosol in Northern China. The mean particle number concentrations of the total particle, as well as the nucleation, Aitken, accumulation and coarse mode were determined to be 1.2 ± 0.9 × 104, 3.6 ± 7.9 × 103, 4.4 ± 3.4 × 103, 3.5 ± 2.8 × 103 and 2 ± 3 cm−3, respectively. A general finding was that the particle number concentration was higher during spring compared to the other seasons. The air mass origin had an important effect on the particle number concentration and new particle formation events. Air masses from northwest (i.e. inner Asia) favored the new particle formation events, while air masses from southeast showed the highest particle mass concentration. Significant diurnal variations in particle number were observed, which could be linked to new particle formation events, i.e. gas-to-particle conversion. During particle formation events, the number concentration of the nucleation mode rose up to maximum value of 104 cm−3. New particle formation events were observed on 36% of the effective measurement days. The formation rate ranged from 0.7 to 72.7 cm−3 s−1, with a mean value of 8.0 cm−3 s−1. The value of the nucleation mode growth rate was in the range of 0.3–14.5 nm h−1, with a mean value of 4.3 nm h−1. It was an essential observation that on many occasions the nucleation mode was able to grow into the size of cloud condensation nuclei (CCN) within a matter of several hours. Furthermore, the new particle formation was regularly followed by a measurable increase in particle mass concentration and extinction coefficient, indicative of a high abundance of condensable vapors in the atmosphere under study