自由基CH（X^2П，α^4∑^-）的光谱数据从头算研究

用分子轨道从头算方法，对CH自由基的基态（X^2П）和低激发态（α^4∑^-）的光谱数据进行了计算。计算结果表明，在基态CH（X^2П）时。在QCISD（T）／6-311G＋＋（3df．3pd）水平上．计算所得的键长R=0.1120981nm，偶极矩μ=1．5891 Debye，υ=2845．43cm^-1均与实验值相吻合，在B3PW91／6-311G＋＋（3df，3pd）理论水平上，计算的基态能量为-38．496143Hartree。误差仅为0．22％；对低激发态CH（α^4∑^-），使用含时的密度泛函方法（TDDPT）和大基组6—311＋＋G（3df，3pd）计算所得的R=0．1094nm，垂直跃迁能量为0．926eV，均与实验结果有较好的吻合。     

Degradation behavior of maleated polyethylene/ground tire rubber thermoplastic elastomers with and without stabilizers

This work investigates the effects of different degradation processes (weathering, thermal ageing and re-extrusion) on maleated polyethylene (MAPE), as well as MAPE/ground tire rubber (GTR) thermoplastic elastomers with and without stabilizers (thermal stabilizer, UVA and HALS). Mechanical characterizations revealed that GTR addition reduced compounds stability against thermal ageing at both 80 and 90 °C. But addition of stabilizers increased thermal stability of the MAPE phase. However, the results suggest that the stabilizers had no effect on the GTR phase. Mechanical characterizations also showed that weathering caused degradation in MAPE, while presence of stabilizers decreased the effects of degradation. Addition of GTR also increased significantly the stability of MAPE against weathering (due to presence of carbon black in GTR). Re-extrusion resulted in lower MAPE modulus (due to decreased molecular weight), while the modulus of GTR filled compounds increased. Re-extrusion also led to decreased GTR average particle size, especially at higher GTR contents. Morphological analyses showed that thermal ageing and re-extrusion did not change significantly blend morphology, but weathering, on the other hand, led to severe degradation of both MAPE and GTR filled compounds surface. Compression set of MAPE/GTR compounds was found to decrease with increasing degradation level (due to crosslinking). Finally, sample density slightly increased with degradation level (also due to crosslinking).     

Untangling complex networks: Risk minimization in financial markets through accessible spin glass ground states

Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.     

Non-existence of vortices in the small density region of a condensate

In this paper, we answer a question raised by Lev Pitaevskii and prove that the ground state of the Gross-Pitaevskii energy describing a Bose-Einstein condensate in a rotationally symmetric trap at low rotation does not have vortices in the low density region. Therefore, the first ground state with vortices has its vortices in the bulk. In fact we prove something stronger, which is that the ground state for the model at low and moderate rotations is equal to the ground state in a condensate with no rotation. This is obtained by proving that for small rotational velocities, the ground state is multiple of the ground state with zero rotation. We rely on sharp bounds of the decay of the wave function combined with weighted Jacobian estimates.     

A critical elliptic problem for polyharmonic operators

In this paper, we study the existence of solutions for a critical elliptic problem for polyharmonic operators. We prove the existence result in some general domain by minimizing on some infinite-dimensional Finsler manifold for some suitable perturbation of the critical nonlinearity when the dimension of domain is larger than critical one. For the critical dimensions, we prove also the existence of solutions in domains perforated with the small holes. Some unstable solutions are obtained at higher level sets by Coron's topological method, provided that the minimizing solution does not exist.     

Front velocity and directed polymers in random medium

We consider a stochastic model of N$N$ evolving particles studied by Brunet and Derrida. This model can be seen as a directed polymer in random medium with N$N$ sites in the transverse direction. Cook and Derrida use heuristic arguments to obtain a formula for the ground state energy of the polymer. We formalize their argument and show that there is an additional term in the formula in the critical case. We also consider a generalization of the model, and show that in the noncritical case the behavior is basically the same, whereas in the critical case a new correction appears.     

甲醇分子(CH3OH)光谱性质的理论计算

研究了气相甲醇分子(CH3OH)基态和激发态性质。在对不同方法基组所得计算结果和实验结果进行比较之后,选用MP2(full)/6-311++G(2d,2p)理论方法进行计算,得到甲醇分子(CH3OH)基态和三重激发态的几何结构、能量以及频率信息;频率计算显示基态和三重态都为稳定构型。从三重态的结构出发,解释了三重态势能面为排斥型势能面的合理性。计算了甲醇分子单重激发态的垂直激发能,比较不同方法不同基组计算的甲醇分子单重激发态的垂直激发能,发现用TDDFT 中的b3p86方法使用6-311++G**基组的计算值和实验值符合得最好。计算得到的甲醇分子在MP2(full)/6-311++G(2d,2p)的绝热电离能和垂直电离能分别为11.18eV和11.32eV;计算得到的绝热电子亲和势与垂直电子亲和势分别为0.888eV和0.893eV。计算结果对实验研究有指导意义。     

Design of data communication and management system for ground test and verification devices of space laser communication

Verification of a space laser communication system's parts or of component-level, terminal-level, and system-level performance using ground test and verification devices on the ground before launch is vital. In this paper, a data communication and management system is proposed, which is an important part of the ground test and verification devices system and manages the test process and impacts on the measurement results directly. We improved the existing hardware buses to make up the hardware part, and also designed the software part. Several typical tests were performed, and the results show that the maximum time delay is less than 50 ms. The developed data communication and management system is demonstrated to be a high-performance system which can meet the requirements in our project.