Purpose In the textile industry, liquid ammonia treatment is an important way to modify the structure of natural fibers. The purpose of this paper is to reveal the diffusion behaviors of liquid ammonia in cellulose. Design/methodology/approach To analysis the diffusion behaviors of liquid ammonia in cellulose, the cellulose model and the system of ammonia and cellulose are built. Infrared spectrum is carried out to test the model of cellulose, which is found to agree with experiment. Diffusion coefficients, free volume and hydrogen bonds are discussed to explain diffusion behaviors. Findings The results demonstrate that diffusion coefficients and free volume of systems rise with increasing temperature. The diffusion coefficients of ammonia are larger than those of water, a result in agreement with free volume. To understand the mechanism of diffusion, the numbers of hydrogen bonds are tracked. It is found that without ammonia, intrachain hydrogen bonds decrease with the increase of temperature, which indicate that the structural stability of cellulose is deteriorated. And the increased interchain hydrogen bonds show that swelling properties of cellulose become better with the increase of temperature. After ammonia treatment, the numbers of intrachain hydrogen bonds remain stable, indicating that the structure stability of cellulose chain is maintained. But, there is a substantial rupture of interchain hydrogen bonds, ammonia molecule destroys the hydrogen bond network between the original cellulose molecular chains, which intensifies the activity of cellulose molecular chains and enlarges the distance between cellulose molecular chains, showing good swelling properties. Originality/value The research findings give a detailed information about the diffusion behaviors of liquid ammonia in cellulose, which provide the theoretical evidence for liquid ammonia treatment.
The yarn vibration causes the yarn tension value to fluctuate, causing a change in the amount of yarn feed, thus causing a deviation of the carpet pile height from the predetermined value. To solve this problem, the sliding mode control algorithm is used to design the sliding mode function and the sliding mode control law. And four variables in the yarn vibration system are controlled by the MATLAB software. For solving the chattering problem of the control law, the sliding mode control law is improved. The fuzzy sliding mode control algorithm based on the quasisliding mode is adopted. The results show that the sliding mode control algorithm is effective, but the sliding mode control force needs to be switched at high frequency and there is severe chattering. The fuzzy sliding mode control algorithm based on quasisliding mode is adopted to achieve better control effect with a smaller force. In addition, the control force does not have high-frequency switching, and the change is relatively stable, which reduces the chattering phenomenon of sliding mode control.
In theory, the cross section is the minimum cut set in the network. For the actual power grid, the transmission cross section is a collection of transmission lines between different regions, which is mainly used for power transmission to achieve the purpose of generating load balance. In this paper, a power grid zoning algorithm is proposed based on the topological structure characteristics and current operation state of the power grid, and the key transmission sections can be directly obtained without depending on the calculation of safety and stability margin. A practical system state partition model and key section sorting method are introduced, and a set of automatic identification method flow of key transmission sections of the system is established by searching for electrical betweenness. The importance of the transmission section is quantitatively evaluated from three angles: the margin from the stability limit, the hub position in the current power flow state, and the impact on the power grid after the power cut-off. The evaluation results can be used as a Reference for decision-making in the planning and reconstruction of the transmission section, safety monitoring, protection configuration, etc.
To control the yarn vibration in a reasonable range and to improve the quality of tufted carpet, it is very important to understand the vibration characteristics of yarn correctly. The transverse vibration equation of yarn is established using Newton’s second law in different paths, and then the yarn vibration characteristic curves in different regions are obtained. Firstly, the yarn path is divided and the optimal constitutive model of tufted carpet yarn is determined. Secondly, the transverse vibration is built by analyzing the force of yarn means. Then, the partial differential equation of yarn vibration is simplified as an ordinary differential equation by the Galerkin truncation method. The equation is solved numerically by using the Runge–Kutta method, obtaining the yarn amplitude in different regions. The vibration characteristics of the yarns after the jacquard parts are emphatically analyzed, and the effects of the speed, tension and damping coefficient on the vibration characteristics of yarns are also discussed. Finally, the results are verified by experiments.
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