The influence of water on protein conformation was investigated by simulating the molecular dynamics of a model protein lysozyme in different water systems. The lysozyme-water system with TIP3P water model and lysozyme-water cluster system with six-ring water model were evaluated. In addition, the radial distribution function of solvent around lysozyme was calculated. It is found that the distribution of water molecules around lysozyme is similar to that of water clusters. The analyses of dihedral angles and disulfide bonds of lysozyme show that the conformation of lysozyme is severely damaged in the lysozyme-water cluster system compared with that in the lysozyme-water system. This difference can be attributed to the formation of larger number of intermolecular hydrogen bonds between lysozyme and water cluster. It is in agreement with the analysis that water clusters can change the degree of denaturation in the process of heat denaturation of lysozyme.
A series of electron donors, including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE), 1,1-cyclopentanedimethanol acetic diester (CPDMAD), 1,1-biethoxymethyl pentane (BEMP), 2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE), were synthesized by diethyl malonate (DEM). The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS), respectively. Furthermore, the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D. Then these electron donors were coordinated with tetrachloro titanium (TiCl4) and chloride magnesium (MgCl2) to obtain the catalysts for the polymerization of propylene. The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID). However, when BEMP was used as ID, the highest catalytic activity is obtained without adding ED, which can reduce production costs and simplify catalytic synthesis. The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.
The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly analyzing the Bode plots of the electrochemical impedance spectroscopy (EIS) data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope (SEM) and scanning probe microscopy (SPM). It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical applications.
Hydroxyapatite bioceramics is simulated by using finite element method (FEM). The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the increase of the angle between crack and horizontal direction, the stress intensity factor K I decreases gradually, but stress intensity factor K II increases at first and then it decreases. The value of K II reaches maximum when the angle between crack and horizontal direction is 45°. K I and K II rise with the increase of porosity, and they are almost the same for the circular and hexagonal holes. For elliptical holes, K I and K II reach maximum when the long axis of ellipse is perpendicular to the loading direction and they reach minimum when the same axis is parallel to the loading direction. Moreover, with the increase of the angle between the long axis and loading direction, K I and K II increase gradually.
A hybrid of ensemble empirical mode decomposition and empirical mode decomposition (EEMD-EMD) is introduced to diagnose the valve-slap vibration signal, which is relative to the dominant combustion knock vibration signal given out by a diesel engine around the top dead center (TDC). The time-frequency representations of intrinsic mode functions (IMFs) decomposed by EEMD-EMD are obtained by adaptive generalized S transform (AGST). A type 493 diesel engine was used for the experiment, and the result indicates that the valve-slap of the diesel engine is serious, and the vibration frequencies are higher than the combustion knock. With EEMD-EMD-AGST approach, the valve-slap can be identified by the vibration analysis of the diesel engine.
To reduce channel noise, fading, and inter-user interference effectively in the chaotic communication systems with multi-user, a blind channel equalization algorithm based on dual unscented Kalman filter algorithm is proposed. Assuming that the coefficients of a multi-input multi-output (MIMO) channel can be described by an autoregressive model, two separate state-space representations are used for the signals and coefficients. Then two unscented Kalman filters are used to estimate chaotic signals and channel coefficients simultaneously. The simulation results indicate that the algorithm can effectively track the coefficients of the multi-path fading channel in chaotic MIMO communication systems at a fast convergence speed.
In the traditional power transmission network planning, deterministic analysis methods are widely used. In such methods, all contingencies are deemed to have the same occurrence probability, which is not reasonable. In this paper, risk assessment is introduced to the process of transmission network planning considering the probabilistic characteristics of contingencies. Risk indices are given to determine the weak points of the transmission network based on local information, such as bus risk, line overload risk, contingency severity. The indices are calculated by the optimal cost control method based on risk theory, which can help planners to quickly determine weak points in the planning and find solution to them. For simplification, only line overload violation is considered. Finally, the proposed method is validated by an IEEE-RTS test system and a real power system in China from two aspects. In the first case, the original system is evaluated by the proposed method to find the weak points, and then four planning schemes are established, among which the best scheme is selected. In the second case, four initial planning schemes are established by combining the experiences of planners, and after the evaluation by using the proposed method, the best planning scheme is improved based on the information of weak points in the initial schemes, and the risk of improved scheme is reduced from 42 531.86 MW·h per year to 4 431.26 MW·h per year.
An adaptive backstepping sliding mode control is proposed for a class of uncertain nonlinear systems with input saturation. A command filtered approach is used to prevent input saturation from destroying the adaptive capabilities of neural networks (NNs). The control law and adaptive updating laws of NNs are derived in the sense of Lyapunov function, so the stability can be guaranteed even under the input saturation. The proposed control law is robust against the disturbance, and it can also eliminate the impact of input saturation. Simulation results indicate that the proposed controller has a good performance.
In this paper, environmental scanning electron microscopy (ESEM) is applied to characterizing the mineral and element distribution of chromite ore processing residue (COPR). The test results show that Cr-bearing brownmillerite occurs in the rim of COPR particle, while hydroandradite with Cr(VI) in its structure presents inside the COPR particle. Periclase and calcite occur in the interstitial area. Element analyses show that Ca, Fe and Al are distributed throughout the COPR particle, and Mg exists mostly in the interstitial area or on the particle surface. A lower content of Cr is evenly distributed in the COPR particle, while slightly higher concentration of Cr occurs inside the particle. It is suggested that it will take a relatively longer time for Cr to migrate out of COPR, especially for hexavalent chromium, so the leaching time and the particle size may be two important factors to affect the release of Cr(VI).
To investigate the mechanical behavior of segmental lining, a three-dimensional numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. Both numerical and test results confirmed that the cracking load, yield and ultimate load were strongly influenced by axial force, and it was also proved that the yield and ultimate load would increase with the increase of reinforcement ratio, but the cracking load was almost not affected. The cracking load, yield and ultimate load are about 28.7%, 500% and 460% larger due to the effect of axial force respectively. The comparison between numerical calculation and test results showed that the finite element analysis results were in good agreement with the test results.
Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure. The geogrid tensions, soil pressures, wall deformations and foundation pressure were measured during model construction and loading. A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term loads. By comparing test data with numerical results, it is shown that the foundation pressure distribution is nonlinear, and the lateral constraint of geogrids for backfill can cause a redistribution of foundation pressure. The curve of soil pressure is outside convex at each step initially, and it is close to the distribution for the case of vertical wall subsequently. The variation trend of geogrid tensions at different heights is obtained. Moreover, the failure mechanism and development mode of potential slip surface in retaining wall are proposed.
The relation between composition operators on the Dirichlet spaces in the open unit disk and derivative weighted composition operators on the Bergman spaces in the open unit disk is investigated firstly, and for a combination of several derivative weighted composition operators which acts on classic Bergman space, the lower bound of its essential norm is estimated in terms of the boundary data of the symbols of d-composition operators. Some similar results about composition operators on the Dirichlet space are also presented. A necessary condition is given to determine the compactness of the combination of several derivative weighted composition operators on Bergman spaces.
In this paper, the network reliability of an actual digital instrument and control system (DICS) network is analyzed by using GO-FLOW methodology (GFM). The evaluations of common-cause failure (CCF) and uncertainty are incorporated. Three significant CCF groups (real time servers, gateways, reactor protection system) and three typical time intervals (10 min, 1 h, and 24 h) are selected in the analysis. It is concluded that the network contribution of CCF accounts for over 68% of the system failure probability. The result indicates that GFM is suitable for the network reliability analysis.