The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated. The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the NaOH concentration or decreasing the particle size of bauxite, which is easy to dissolve under atmospheric pressure. The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established, and the corresponding activation energies were calculated. The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution, the diffusion process of which is the rate-controlling step.

The gasification industries make use of biomass residue as feedstock to produce synthesis gas, but the gasification of this waste biomass generates tons of ash everyday. Performance properties and agglomeration behavior of corncob ash (CCA) collected from the gasification of corncobs in a pilot-scale gasification station were investigated by using some experimental methods. Based on the chemical composition results, the agglomeration tendency of CCA from combustion and gasification process was also analyzed. Chemical analysis shows that the fly ash is mainly composed of inorganic matters formed by K, Mg, Ca, Na, Fe, Al, S, etc. The agglomeration characteristics indicate that the slagging degree increases with the increase of ashing temperature, and the slagging tendency of these CCA samples from gasification or combustion is different with various slagging indices. All CCA samples from combustion or gasification can cause slagging/fouling problems in thermal conversion systems. The applications of CCA are closely related to its performances, and CCA has the potential to be used in various fields, for example, as a material for ceramic products and activated carbon, as an adsorbent, as a crude fertilizer, and as a structural material.

In order to present the microstructures of dynamic recrystallization (DRX) in different deformation zones of hot extruded NiTi shape memory alloy (SMA) pipe coupling, a simulation approach combining finite element method (FEM) with cellular automaton (CA) was developed and the relationship between the macroscopic field variables and the microscopic internal variables was established. The results show that there exists a great distinction among the microstructures in different zones of pipe coupling because deformation histories of these regions are diverse. Large plastic deformation may result in fine recrystallized grains, whereas the recrystallized grains may grow very substantially if there is a rigid translation during the deformation, even if the final plastic strain is very large. As a consequence, the deformation history has a significant influence on the evolution path of the DRX as well as the final microstructures of the DRX, including the morphology, the mean grain size and the recrystallization fraction.

The hot deformation behavior of Al-6.2Zn-0.70Mg-0.30Mn-0.17Zr alloy and its microstructural evolution were investigated by isothermal compression test in the deformation temperature range between 623 and 773 K and the strain rate range between 0.01 and 20 s^-1. The results show that the flow stress decreased with decreasing strain rate and increasing deformation temperature. At low deformation temperature (≤673 K) and high strain rate (≥1 s^-1), the main flow softening was caused by dynamic recovery; conversely, at higher deformation temperature and lower strain rate, the main flow softening was caused by dynamic recrystallization. Moreover, the slipping mechanism transformed from dislocation glide to grain boundary sliding with increasing the deformation temperature and decreasing the strain rate. According to TEM observation, numerous Al₃Zr particles precipitated in matrix, which could effectively inhibit the dynamic recrystallization of the alloy. Based on the processing map, the optimum processing conditions for experimental alloy were in deformation temperature range from 730 K to 773 K and strain rate range from 0.033 s^-1 to 0.18 s^-1 with the maximum efficiency of 39%.

With the development of digital information technologies, robust watermarking framework is taken into real consideration as a challenging issue in the area of image processing, due to the large applicabilities and its utilities in a number of academic and real environments. There are a wide range of solutions to provide image watermarking frameworks, while each one of them is attempted to address an efficient and applicable idea. In reality, the traditional techniques do not have sufficient merit to realize an accurate application. Due to the fact that the main idea behind the approach is organized based on contourlet representation, the only state-of-the-art materials that are investigated along with an integration of the aforementioned contourlet representation in line with watermarking framework are concentrated to be able to propose the novel and skilled technique. In a word, the main process of the proposed robust watermarking framework is organized to deal with both new embedding and de-embedding processes in the area of contourlet transform to generate watermarked image and the corresponding extracted logo image with high accuracy. In fact, the motivation of the approach is that the suggested complexity can be of novelty, which consists of the contourlet representation, the embedding and the corresponding de-embedding modules and the performance monitoring including an analysis of the watermarked image as well as the extracted logo image. There is also a scrambling module that is working in association with levels-directions decomposition in contourlet embedding mechanism, while a decision maker system is designed to deal with the appropriate number of sub-bands to be embedded in the presence of a series of simulated attacks. The required performance is tangibly considered through an integration of the peak signal-to-noise ratio and the structural similarity indices that are related to watermarked image. And the bit error rate and the normal correlation are considered that are related to the extracted logo analysis, as well. Subsequently, the outcomes are fully analyzed to be competitive with respect to the potential techniques in the image colour models including hue or tint in terms of their shade, saturation or amount of gray and their brightness via value or luminance and also hue, saturation and intensity representations, as long as the performance of the whole of channels are concentrated to be presented. The performance monitoring outcomes indicate that the proposed framework is of significance to be verified.

Because of various error factors, the detecting errors in the real-time experimental data of the wear depth affect the accuracy of the detecting data. The self-made spherical plain bearing tester was studied, and its testing principle of the wear depth of the spherical plain bearing was introduced. Meanwhile, the error factors affecting the wear-depth detecting precision were analyzed. Then, the comprehensive error model of the wear-depth detecting system of the spherical plain bearing was built by the multi-body system theory (MBS). In addition, the thermal deformation of the wear-depth detecting system caused by varying the environmental temperature was detected. Finally, according to the above experimental parameters, the thermal errors of the related parts of the comprehensive error model were calculated by FEM. The results show that the difference between the simulation value and the experimental value is less than 0.005 mm, and the two values are close. The correctness of the comprehensive error model is verified under the thermal error experimental conditions.

The effect of fin attachment on the thermal stress reduction of exhaust manifold of an off road diesel engine (Komatsu HD325-6) was investigated. For doing this, coupled thermo-fluid-solid analysis of exhaust manifold of the off road diesel engine was carried out. The thermal analysis, including thermal flow, thermal stress, and the thermal deformation of the manifold was investigated. The flow inside the manifold was simulated and then its properties including velocity, pressure, and temperature were obtained. The flow properties were transferred to the solid model and then the thermal stresses and the thermal deformations of the manifold under different operating conditions were calculated. Finally, based on the predicted thermal stresses and thermal deformations of the manifold body shell, two fin types as well as body shell thickness increase were applied in the critical induced thermal stress area of the manifold to reduce the thermal stress and thermal deformation. The results of the above modifications show that the combined modifications, i.e. the thickness increase and the fin attachment, decrease the thermal stresses by up to 28% and the contribution of the fin attachment in this reduction is much higher compared to the shell thickness increase.

The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials. To study the strength characteristics of loess soil reinforced by modified polypropylene (MPP) fiber and cement, samples were prepared with six different fiber contents, three different cement contents, three different curing periods and three kinds of fiber length. The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength (UCS), the splitting tensile strength and the compressive resilient modulus. The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days. With an increase in cement content, the specimens exhibited brittle fracture. However, the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic. The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm, for which the unconfined compressive strength and tensile strength reached their maxima. Based on the analysis of failure properties, cement-reinforced loess specimens were susceptible to brittle damage under pressure, and the effect of modified polypropylene fiber as the connecting “bridge” could help the specimens achieve a satisfactory level of ductility when under pressure.

This study proposes a graphical user interface (GUI) based on an enhanced bacterial foraging optimization (EBFO) to find the optimal locations and sizing parameters of multi-type DFACTS in large-scale distribution systems. The proposed GUI based toolbox, allows the user to choose between single and multiple DFACTS allocations, followed by the type and number of them to be allocated. The EBFO is then applied to obtain optimal locations and ratings of the single and multiple DFACTS. This is found to be faster and provides more accurate results compared to the usual PSO and BFO. Results obtained with MATLAB/Simulink simulations are compared with PSO, BFO and enhanced BFO. It reveals that enhanced BFO shows quick convergence to reach the desired solution there by yielding superior solution quality. Simulation results concluded that the EBFO based multiple DFACTS allocation using DSSSC, APC and DSTATCOM is preferable to reduce power losses, improve load balancing and enhance voltage deviation index to 70%, 38% and 132% respectively and also it can improve loading factor without additional power loss.

An extended-state-observer (ESO) based predictive control scheme is proposed for the autopilot of lunar landing. The slosh fuel masses exert forces and torques on the rigid body of lunar module (LM), such disturbances will dramatically undermine the stability of autopilot system. The fuel sloshing dynamics and uncertainties due to the time-varying parameters are considered as a generalized disturbance which is estimated by an ESO from the measured attitude signals and the control input signals. Then a continuous-time predictive controller driven by the estimated states and disturbances is designed to obtain the virtual control input, which is allocated to the real control actuators according to a deadband logic. The 6-DOF simulation results reveal the effectiveness of the proposed method when dealing with the fuel sloshing dynamics and parameter perturbations.

Noise-assisted multivariate empirical mode decomposition (NA-MEMD) is suitable to analyze multichannel electroencephalography (EEG) signals of non-stationarity and non-linearity natures due to the fact that it can provide a highly localized time-frequency representation. For a finite set of multivariate intrinsic mode functions (IMFs) decomposed by NA-MEMD, it still raises the question on how to identify IMFs that contain the information of inertest in an efficient way, and conventional approaches address it by use of prior knowledge. In this work, a novel identification method of relevant IMFs without prior information was proposed based on NA-MEMD and Jensen-Shannon distance (JSD) measure. A criterion of effective factor based on JSD was applied to select significant IMF scales. At each decomposition scale, three kinds of JSDs associated with the effective factor were evaluated: between IMF components from data and themselves, between IMF components from noise and themselves, and between IMF components from data and noise. The efficacy of the proposed method has been demonstrated by both computer simulations and motor imagery EEG data from BCI competition IV datasets.

A novel performance model of losses of pump was presented, which allows an explicit insight into the losses of various friction pairs of pump. The aim is to clarify that to what extent the hydro-mechanical losses affect efficiency, and to further gain an insight into the variation and distribution characteristics of hydro-mechanical losses over wide operating ranges. A good agreement is found in the comparisons between simulation and experimental results. At rated speed, the hydro-mechanical losses take a proportion ranging from 87% to 89% and from 68% to 97%, respectively, of the total power losses of pump working under 5 MPa pressure conditions, and 13% of full displacement conditions. Furthermore, within the variation of speed ranging from 48% to 100% of rated speed, and pressure ranging from 14% to 100% of rated pressure, the main sources of hydro-mechanical losses change to slipper swash plate pair and valve plate cylinder pair at low displacement conditions, from the piston cylinder pair and slipper swash plate pair at full displacement conditions. Besides, the hydro-mechanical losses in ball guide retainer pair are found to be almost independent of pressure. The derived conclusions clarify the main orientations of efforts to improve the efficiency performance of pump, and the proposed model can service for the design of pump with higher efficiency performance.

Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections. For the special geometry characteristic, the beam was modelled as the combination of long equal-length uniform Euler-Bernoulli beam segments and short equal-length uniform Timoshenko beam segments alternately. By using continuity conditions, the hybrid beam unit (ETE-B) consisting of Euler-Bernoulli beam, Timoshenko beam and Euler-Bernoulli beam in sequence was developed. Classical boundary conditions of pinned-pinned, clamped-clamped and clamped-free were considered to obtain the natural frequencies. Numerical examples of the equal-length composite beam with 1, 2 and 3 ETE-B units were presented and compared with the equal-length and equal-cross-section Euler-Bernoulli beam, respectively. The work demonstrates that natural frequencies of the composite beam are larger than those of the Euler-Bernoulli beam, which in practice, is the interpretation that the inner-welded plate can strengthen a hollow beam. In this work, comparisons with the finite element calculation were presented to validate the ETE-B model.

A great number of pipelines in China are in unsatisfactory condition and faced with problems of corrosion and cracking, but there are very few approaches for underwater pipeline detection. Pipeline detection autonomous underwater vehicle (PDAUV) is hereby designed to solve these problems when working with advanced optical, acoustical and electrical sensors for underwater pipeline detection. PDAUV is a test bed that not only examines the logical rationality of the program, effectiveness of the hardware architecture, accuracy of the software interface protocol as well as the reliability and stability of the control system but also verifies the effectiveness of the control system in tank experiments and sea trials. The motion control system of PDAUV, including both the hardware and software architectures, is introduced in this work. The software module and information flow of the motion control system of PDAUV and a novel neural network-based control (NNC) are also covered. Besides, a real-time identification method based on neural network is used to realize system identification. The tank experiments and sea trials are carried out to verify the feasibility and capability of PDAUV control system to complete underwater pipeline detection task.

The problem of discrete-time model identification of industrial processes with time delay was investigated. An iterative and separable method is proposed to solve this problem, that is, the rational transfer function model parameters and time delay are alternately fixed to estimate each other. The instrumental variable technique is applied to guarantee consistent estimation against measurement noise. A noteworthy merit of the proposed method is that it can handle fractional time delay estimation, compared to existing methods commonly assuming that the time delay is an integer multiple of the sampling interval. The identifiability analysis for time delay is addressed and correspondingly, some guidelines are provided for practical implementation of the proposed method. Numerical and experimental examples are presented to illustrate the effectiveness of the proposed method.

For the characteristics of the continuous stirred-tank reactor (CSTR) with coil and jacket cooling system, a CSTR temperature dual control solution based on the analysis of the CSTR exothermic reaction control characteristic was proposed for an organic material polymerization production. The control solution has passive fault-tolerant ability for the jacket cooling water cutting off fault and active fault-tolerant potential for the coil cooling water cutting off fault, and it has good control ability, high saving energy and reducing consumption performance. Fault detection and diagnosis and fault-tolerant control strategy are designed for the coil cooling fault to achieve the active fault-tolerant control function. The CSTR temperature dual control, process fault detection and diagnosis and active fault-tolerant control were full integrated into the CSTR temperature fault-tolerant control system, which achieve fault tolerance control of CSTR temperature for any severe malfunction of jacket cooling or coil cooling cutting off, and the security for CSTR exothermic reaction is improved. Finally, the effectiveness of this system was validated by semi-physical simulation experiment.

A new modeling and monitoring approach for multi-mode processes is proposed. The method of similarity measure(SM) and kernel principal component analysis (KPCA) are integrated to construct SM-KPCA monitoring scheme, where SM method serves as the separation of common subspace and specific subspace. Compared with the traditional methods, the main contributions of this work are: 1) SM consisted of two measures of distance and angle to accommodate process characters. The different monitoring effect involves putting on the different weight, which would simplify the monitoring model structure and enhance its reliability and robustness. 2) The proposed method can be used to find faults by the common space and judge which mode the fault belongs to by the specific subspace. Results of algorithm analysis and fault detection experiments indicate the validity and practicability of the presented method.

This work focuses on transient thermal behavior of radial fins of rectangular, triangular and hyperbolic profiles with temperature-dependent properties. A hybrid numerical algorithm which combines differential transformation (DTM) and finite difference (FDM) methods is utilized to theoretically study the present problem. DTM and FDM are applied to the time and space domains of the problem, respectively. The accuracy of this method solution is checked against the numerical solution. Then, the effects of some applicable parameters were studied comparatively. Since a broad range of governing parameters are investigated, the results could be useful in a number of industrial and engineering applications.

In order to study the dynamic response of concrete-filled steel tube (CFST) columns against blast loads, a simplified model is established utilizing the equivalent single-degree-of-freedom (SDOF) method, which considers the non-uniform distribution of blast loads on real column and the axial load-bending moment (P-M) interaction of CFST columns. Results of the SDOF analysis compare well with the experimental data reported in open literature and the values from finite element modeling (FEM) using the program LS-DYNA. Further comparisons between the results of SDOF and FEM analysis show that the proposed model is effective to predict the dynamic response of CFST columns with different blast conditions and column details. Also, it is found that the maximum responses of the columns are overestimated when ignoring the non-uniformity of blast loads, and that neglecting the effect of P-M interaction underestimates the maximum response of the columns with large axial load ratio against close range blast. The proposed SDOF model can be used in the design of the blast-loaded CFST columns.

Temporal-spatial cross-correlation analysis of non-stationary wind speed time series plays a crucial role in wind field reconstruction as well as in wind pattern recognition. Firstly, the near-surface wind speed time series recorded at different locations are studied using the detrended fluctuation analysis (DFA), and the corresponding scaling exponents are larger than 1. This indicates that all these wind speed time series have non-stationary characteristics. Secondly, concerning this special feature (i.e., non-stationarity) of wind signals, a cross-correlation analysis method, namely detrended cross-correlation analysis (DCCA) coefficient, is employed to evaluate the temporal-spatial cross-correlations between non-stationary time series of different anemometer pairs. Finally, experiments on ten wind speed data synchronously collected by the ten anemometers with equidistant arrangement illustrate that the method of DCCA cross-correlation coefficient can accurately analyze full-scale temporal-spatial cross-correlation between non-stationary time series and also can easily identify the seasonal component, while three traditional cross-correlation techniques (i.e., Pearson coefficient, cross-correlation function, and DCCA method) cannot give us these information directly.

A unified constitutive model is proposed to describe the mechanical behavior of weak sandstone at different time scales. The instantaneous behavior of this material is characterized by the Drucker-Prager elastoplastic model, while the time-dependent deformation is described in terms of the microstructure evolution. This evolution is numerically simulated by progressive degradation of the elastic modulus and failure strength of the material. The proposed model is used to simulate the instantaneous triaxial compression and the multi-loading creep tests. Generally, good concordance is obtained between numerical simulations and experimental data. The proposed model is capable of describing the main features of these rocks, particularly irreversible deformations, pressure dependency, volumetric transition between compaction and dilatancy, and creep behavior.

The differential cubature solution to the problem of a Mindlin plate lying on the Winkler foundation with two simply supported edges and two clamped edges was derived. Discrete numerical technology and shape functions were used to ensure that the solution is suitable to irregular shaped plates. Then, the mechanical model and the solution were employed to model the protection layer that isolates the mining stopes from sea water in Sanshandao gold mine, which is the first subsea mine of China. Furthermore, thickness optimizations for the protection layers above each stope were conducted based on the maximum principle stress criterion, and the linear relations between the best protection layer thickness and the stope area under different safety factors were regressed to guide the isolation design. The method presented in this work provides a practical way to quickly design the isolation layer thickness in subsea mining.

Homogeneity and heterogeneity are two totally different concepts in nature. At the particle length scale, rocks exhibit strong heterogeneity in their constituents and porosities. When the heterogeneity of porosity obeys the random uniform distribution, both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field. The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method. The related computational simulation results have demonstrated that: 1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field, an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front. 2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock. 3) The greater the mean value of porosities in the initial porosity field, the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems. This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.

This work deals with super-harmonic responses and the stabilities of a gear transmission system of a high-speed train under the stick-slip oscillation of the wheel-set. The dynamic model of the system is developed with consideration on the factors including the time-varying system stiffness, the transmission error, the tooth backlash and the self-excited excitation of the wheel-set. The frequency-response equation of the system at super-harmonic resonance is obtained by the multiple scales method, and the stabilities of the system are analyzed using the perturbation theory. Complex nonlinear behaviors of the system including multi-valued solutions, jump phenomenon, hardening stiffness are found. The effects of the equivalent damping and the loads of the system under the stick-slip oscillation are analyzed. It shows that the change of the load can obviously influence the resonance frequency of the system and have little effect on the steady-state response amplitude of the system. The damping of the system has a negative effect, opposite to the load. The synthetic damping of the system composed of meshing damping and equivalent damping may be less than zero when the wheel-set has a large slippage, and the system loses its stability owing to the Hopf bifurcation. Analytical results are validated by numerical simulations.

A novel vacuum ice slurry producing system with jet-pumps was proposed to deal with the problems of high energy consumption and ice blockage. In this novel system, one steam driven by a jet-pump was used to create vacuum in a hermetic vessel where water was sprayed through a nozzle to produce ice slurry, while the other steam was used to provide enough cold energy to make the left vapor in the hermetic vessel condense. Mathematical models of this novel system were established and theoretical simulation on the performance characteristics was also implemented based on the MATLAB program. Results show that the novel system is feasible and practicable, and the system performance is affected by many factors, such as the temperature of the generators, condensing temperature, evaporation temperature, and the cooling load of the refrigerator sub-system. The findings are helpful to improve the performance of ice slurry producing system.