STOCHASTIC MODEL OF PERIODIC OPERATION PERFORMANCE FOR THE CONTINUOUS COUNTER－CURRENT ADSORPTION PROCESS

A stochastic model is developed to predict the peniodic operation performance ofthe continuous counter-current adsorption process. The model takes into account theeffects of random backmixing of particles, axial dispersion of liquid phase, liquid- film mass transfer, intraparticle diffusion and panticle shape, and can revealclearly the behavior of solid and liquid phase in adsorption process. The simulation results agree with the experimental data rather well.

Role of Periodic Input Composition and Sweeping Gas for Improvement of Hydrogen Production in a Palladium Membrane Reactor by Partial Oxidation of Methane

The partial oxidation of methane under periodic operation over Ni/y/-Al2O3 catalyst was investigated in a Pd-membrane reactor. The effects of key parameters such as the inlet composition and the sweeping, gas on methane conversion and the hydrogen recovery are numerically estalallshed with two penodtc input ttmctlons. In order to analyze the effect of the inputs modulation, the reaction was performed under low steam to methane ratio at a mod-erate temperature and pressure. It was obtained that to achieve process intensification is to operate the process in a periodic way. The main results show that the periodic input functions can improve the performance of the process compared to the optimal steady state operation. Moreover, there is an optimum amplitude of manipulated inputs leads to a maximum of hydrogen recovery. It is noteworthy that the comparison between the predicted performancevia the sinusoidal and the＇square ways show that the better＇average performance was obtainedwith the square way.

Positive Periodic Solutions for Prey-predator Model with Saturation

By the theory of periodic parabolic operators, Shauder estimates and bifurcation, the existence of positive periodic solutions for periodic prey-predator model with saturation is discussed. The necessary and sufficient conditions to coexistence of periodic system are obtained.

Existence and Uniqueness of Positive Periodic Solutions for First-order Functional Differential Equations

In this paper, we prove the existence and uniqueness of positive periodic solutions for first-order functional differential equation y＇（t） = α（t）y（t） ＋ f（t, y（t -τ-（t））） ＋ g（t）by using two fixed point theorems of general α-concave operators and homogeneous operators in ordered Banach spaces.

Seepage field distribution and water inflow laws of tunnels in water-rich regions

Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.

On Problems of Multicomponent System Maintenance Modelling

We present an overview of some recent developments in the area of mathematical modeling of maintenance decisions for multi-unit systems. The emphasis is on three main groups of multicomponent maintenance optimization models： the block replacement models, group maintenance models, and opportunistic maintenance models. Moreover, an example of a two-unit system maintenance process is provided in order to compare various maintenance policies.

Analysis and Research on the Thermal Environment of Subway Stations in Wuhan

With the rapid advancement of urban construction,urban subway construction in China has entered an advanced development stage and the thermal environment of subway stations has become a key factor affecting passengers'thermal comfort.To further understand the actual situation of the thermal environment of subway stations,field measurement and CFD simulation were carried out on a subway station hall in Wuhan from July to August 2021,and the thermal environment changes and influencing factors during subway operation were compared and analyzed.The present situation of the thermal environment in subway stations was analyzed,and some suggestions and measures for improving the thermal environment were put forward.

The hydrological effect between Jingjiang River and Dongting Lake during the initial period of Three Gorges Project operation

Based on the measured hydrological data from 1951 to 2008, the chain hydrological effect between Jingjiang River and Dongting Lake is analyzed by comparative method after the Three Gorges Project operation. The result indicates that 1） the scouring amount in Jing- jiang River made up 78.9% of the total from Yichang to Chenglingji, and its average scouring intensity was higher than the latter; 2） the water and sand diversion rates at the three outlets of the Jingjiang River were reduced by 2.33% and 2.78% separately; 3） the proportion of multi-year average runoff and sediment through the three outlets in the total into the Dongting Lake decreased by 7.7% and 24.4% respectively; 4） in Dongting Lake, the speed of sediment accumulation was lowered by 26.7%, in flood season, the runoff amount was 20.2% less than the multi-year average value, leading to seasonal scarcity of water year by year. The former prolonged the lake life, while the latter induced droughts in summer and fall in successive years, shortage of drinking and industrial water, shipping insecurity, as well as ecological problems such as decrease of birds and quick increase of Microtus fortis; 5） The multi-year average values of sediment and flood transporting capacity at the lake outlet were respec- tively increased by 26.6% and 3.7%, the adapt to the new change of the river-lake embankments were protected effectively. Then, to relation, some suggestions were put forward, such as optimizing further operation program of the Three Gorges Reservoir, reexamining the idea of river and lake regulation, and maintaining connection of the river and the lake.

A New Treatment for Some Periodic Schr?dinger Operators Ⅱ: The Wave Function

Following the approach of our previous paper we continue to study the asymptotic solution of periodic Schrodinger operators. Using the eigenvalues obtained earlier the corresponding asymptotic wave functions are derived. This gives further evidence in favor of the monodromy relations for the Floquet exponent proposed in the previous paper. In particular, the large energy asymptotic wave functions are related to the instanton partition function of N = 2 supersymmetric gauge theory with surface operator. A relevant number theoretic dessert is appended.

Global structure of spectra of periodic non-Hermitian Jacobi operators

We give global structure of spectra of periodic non-Hermitian Jacobi operators by the discriminant and its stationary points. We also give necessary and sufficient conditions for real spectra and single interval spectra.