Zhang Li-Li

Influence of rotational isomerism on two-photon absorption properties of FTC chromophores

The influence of rotational isomerism on the two-photon absorption (TPA) of FTC chromophores has been investigated using the quadratic response theory with the B3LYP functional. Eight rotamers induced by three rotatable single bonds in the molecule are fully optimized, and it is found that their conformational energies are nearly degenerate. Our calculations demonstrate that rotational isomerism has an important effect on the TPA cross sections. For a certain rotamer, the maximum TPA cross section is enhanced significantly. In addition, in the longer wavelength region, the rotational isomerism could lead to a large shift of the TPA position.

An Inverse Optimization Model for Human Resource Allocation Problem Considering Competency Disadvantage Structure

Most of serious and major accidents that happened during the production procedure of process industry are caused by improper equipment operations, which is further owing to inappropriate human resources allocation and ignorance of individual competencies differences. In order to take both of competency disadvantage and adjustment requirement into consideration, we use an inverse optimization method to solve a human resource allocation problem, and furthermore, adjust equipment operating parameters to make the per-defined settings optimized, such as the total number of jobs, security-related parameters and so on.In the solving process, firstly a standard competence hierarchy system is conducted; secondly we propose an assessment method according to disadvantage structure; thirdly we use inverse optimization method to solve the problem and optimize the predefined allocation plan. Lastly, we give an example to prove its feasibility and effectiveness. In this paper a novel formulation of human resource allocation problem is proposed, in which some of main individual characteristics are considered and described mathematically, including psychology, behaviour and characteristics diged from them such as weakness. The other contribution of this paper is using inverse optimization to adjust parameters based on the given ideal allocation plan. Both of these propositions have a positive significance on promoting development and security construction for process industries.This research incorporates the academic thinking of inverse optimization, it not only puts psychology and behavior into optimization model, but also data mines weakness characteristics under the psychology and behavior data, and find a new way to introducing the weakness characteristics into decision making model. It provides a new thought for the following decision making problem, that is the ideal decision plan is known, and optimization parameters are changeable. It promotes the combining of psychology, behavior and operations research, it is good for process industries to develop in a safety and efficiency way.

Simulations of the flipping images and microparameters of molecular orientations in liquids according to the molecule string model

The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, and at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion is of reference significance for solving and simulating the multi-state MS model.

Monte Carlo simulations of the relaxation dynamics of the spatial relaxation modes in the molecule-string model

According to the molecule-string model for glass transition, a more exact Monte Carlo protocol to simulate all the spatial relaxation modes (SRMs) of the string are proposed. The variations of the simulated relaxation times of the SRMs with temperature and string length are consistent with the predictions of the string relaxation equation of the model, i.e. the theretical predictions and the simulation results verify each other. It should be pointed out that the necessary condition of molecule string used as a collective unit in liquid is that the qualitative characteristics of the SRMs cannot be changed when the inter-string interactions are taken into account. This needs to study the coupling between the SRMs, but till now, the corresponding exact solutions have not been achieved, and only the self-consistent relaxation mean-field method is vailable. Therefore, the present simulation protocol will provide a necessary basis to study the coupling between the SRMs of neighboring strings, including the feasibility of the mean-field method.

Numerical simulation of super-short pulsed discharge in helium with particle-in-cell Monte Carlo collisions technique

This paper reports that a simulation of glow discharge in pure helium gas at the pressure of 1.333 × 103 Pa under a high-voltage nanosecond pulse is performed by using a one-dimensional particle-in-cell Monte Carlo collisions (PIC-MCC) model. Numerical modelling results show that the cathode sheath is much thicker than that of anode during the pulse discharge, and that there exists the phenomenon of field reversal at relative high pressures near the end of the pulse, which results from the cumulative positive charges due to their finite mobility during the cathode sheath expansion. Moreover, electron energy distribution function (EEDF) and ion energy distribution function (IEDF) have been also observed. In the early stage of the pulse, a large amount of electrons can be accelerated above the ionization threshold energy. However, in the second half of the pulse, as the field in bulk plasma decreases and thereafter the reverse field forms due to the excessive charges in cathode sheath, although the plasma density grows, the high energy part of EEDF decreases. It concludes that the large volume non-equilibrium plasmas can be obtained with high-voltage nanosecond pulse discharges.