Growth kinetics of the most stable polymorph of calcium carbonate, calcite, has been studied in seeded stirred batch experiments in MEG-water solutions at 40 °C and 70 °C, conditions relevant for the processing of natural gas. It was found that MEG changes the growth order from two in pure water to one in solvent mixtures of MEG and water. Assuming parabolic growth (growth order is equal to two), it could be shown that MEG decreases the growth rate constant for calcite from 0.52 nm/s to 0.11 nm/s (70 °C) when the MEG-content is increased from 0 wt% MEG to 65 wt% MEG. Decreasing the temperature from 70 °C to 40 °C has a similar effect on the growth rate constant as raising the level of MEG to 65 wt%.
Enantiomers (R(+) and S(−)), RS-racemate (double compound) and (R+S)-conglomerate (mechanical mixture of enantiomers) of malic acid C4H6O5 have been investigated by means of X-ray diffractometry and high temperature X-ray diffraction method. The RS-racemate was found to be able to form three polymorphic modifications, which we denominated as M1 (monoclinic, space group P21/c), M2 (monoclinic, space group Cc), and Tc (triclinic, space group P-1), the latter modification having been unknown before. Modification Tc was also described, and its Xray diffraction characteristics, including interplanar spacings d, hkl indices, unit cell parameters, were defined. In addition, X-ray diffraction characteristics for both reported earlier M1 and M2 monoclinic polymorphic modifications were measured with higher accuracy. The ability of RS-racemate to form one of the above three modifications (M1, M2, and Tc) or their mixtures containing various proportions and combinations of the components (M1+M2, M1+Tc, or M2 +Tc) was found to depend on the type of crystallization medium (a melt, aqueous medium, ethanol or acetone solution), crystallization rate (from 2–3 minutes to 4 months), and crystallization temperature. Heating S-enantiomer and M1 RS-racemate up to their respective melting points (100 °C and 124 °C, correspondingly) only made them undergo thermal deformations, while heating (R+S)-conglomerate in the temperature range of 96–110 °C resulted in its homogenization to form M2 RS-racemate, which, near the melting point (118 °C), namely, in the range of 112–116 °C, was transformed into M1 RS-racemate.
The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization. EN data were analyzed using phase space reconstruction theory. With the correlation dimensions obtained from the phase space reconstruction, the chaotic behavior of EN was quantitatively evaluated. The results show that both electrochemical potential noise (EPN) and electrochemical current noise (ECN) have chaotic properties. The correlation dimensions of EPN increase with corrosion extent, while those of ECN seem nearly unchanged. The increased correlation dimensions of EPN during the degradation process are associated with the increased susceptibility to local corrosion.
A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider. Heat generated by PEMFC is used as the propulsion power of the glider, and the electricity is used in the control and sensor system. An electric energy storage system (ESS) is required which possesses high power density with good cycle life. Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices. Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system. Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS.
Viscosity reduction is an important process in mining heavy oil. To predict the temperature variation and viscosity variation of heavy oil in flow direction, computational fluid dynamics(CFD) was adopted to simulate the process of heat transfer and flow in this paper. Moreover, an objective function, namely viscosity reduction efficiency, was established to analyze the effect of viscosity reduction. The results indicate that circulating hot water can reduce viscosity significantly, and that the effect of viscosity reduction depends on the inlet temperature and inlet volumetric flow rate of hot water. There is a maximum temperature of heavy oil in flow direction. With the inlet volumetric flow rate of 2.0 m3/h and the inlet temperatures of 60,°C, 70,°C and 80,°C, viscosity reduction efficiencies are 94.6%, 96.7% and 97.3%, respectively. With the inlet temperature of 70,°C and the volumetric flow rates of 1.5 m3/h, 2.0 m3/h and 2.5 m3/h, viscosity reduction efficiencies are 94.4%, 96.7% and 97.2%, respectively.
To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement, two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading, which imitated low to moderate earthquake force. The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity, displacement, ductility, hysteretic curve, stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region. With the damage estimation model, the accumulated damage was analyzed. The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form. The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior, ductility and hysteretic characteristic. All specimens were damaged with gradual stiffness degeneration. In addition, X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage. The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications. The test value is higher than the calculated value, which indicates that the formula is safe for the design of specially shaped column joints.
A dynamic velocity feed-forward compensation control (DVFCC) approach with RBF neural network (RBF-NN) dynamic model identification was presented for the adaptive trajectory tracking of industrial robots. The proposed control approach combined the advantages of traditional feedback closed-loop position control and computed torque control based on inverse dynamic model. The feed-forward compensator used a nominal robot dynamics as accurate dynamic model and on-line identification with RBF-NN as uncertain part to improve dynamic modeling accuracy. The proposed compensation was applied as velocity feed-forward by an inverse velocity controller that can convert torque signal into velocity in the standard industrial controller. Then, the need for a torque control interface was avoided in the real-time dynamic control of industrial robot. The simulations and experiments were carried out on a gas cutting manipulator. The results show that the proposed control approach can reduce steady-state error, suppress overshoot and enhance tracking accuracy and efficiency in joint space and Cartesian space, especially under highspeed condition.
Thin plates of 21% Cr ferritic stainless steel welded by pulsed gas tungsten arc welding at different pulse frequencies were investigated for the microstructure characteristics and hardness behavior. The welds contained columnar grains in the outer part and fine equiaxed grains in the central region due to the pulsed process.
Property path is the latest navigational extension of the standard query language SPARQL 1.1 for the Semantic Web. However, in the existing SPARQL query systems which support property path, the query efficiency is very low and does not support reasoning. This paper proposes a new existential semantics which has polynomial-time evaluation complexity and an equivalent relationship with the current semantics, and transforms the property path expressions to the extended nested regular expressions based on the existential semantics and proves the semantic equivalence after the transformation considering the RDFS semantics. The property path query engine is achieved by implementing the nested regular expressions algorithm and the transformation rules from the property path expressions to the nested regular expressions, which maintains the syntax simplicity of property path and the goal-oriented polynomial-time reasoning to avoid computing the RDF graph closure. The experiment results not only show the characteristics of query engine based on the existential semantics in efficiency and reasoning, but also further validate the equivalence between the results based on current semantics and those based on the existential semantics for property path after the removal of duplicate values.
An addition scheme applicable to time-delay integration (TDI) CMOS image sensor is proposed, which adds signals in the charge domain in the pixel array. A two-shared pixel structure adopting two-stage charge transfer is introduced, together with the rolling shutter with an undersampling readout timing. Compared with the conventional TDI addition methods, the proposed scheme can reduce the addition operations by half in the pixel array, which decreases the power consumption of addition circuits outside the pixel array. The timing arrangement and pixel structure are analyzed in detail. The simulation results show that the proposed pixel structure can achieve the charge addition with negligible nonlinearity, therefore the power consumption of the periphery addition circuits can be reduced by half theoretically.
Traditional studies on integrated statistical process control and engineering process control (SPC-EPC) are based on linear autoregressive integrated moving average (ARIMA) time series models to describe the dynamic noise of the system. However, linear models sometimes are unable to model complex nonlinear autocorrelation. To solve this problem, this paper presents an integrated SPC-EPC method based on smooth transition autoregressive (STAR) time series model, and builds a minimum mean squared error (MMSE) controller as well as an integrated SPC-EPC control system. The performance of this method for checking the trend and sustained shift is analyzed. The simulation results indicate that this integrated SPC-EPC control method based on STAR model is effective in controlling complex nonlinear systems.