Inverse gas chromatographic technique(IGC) was attempted as a new approach to follow the chem-ical changes that occur during lubricating base oil oxidation.Three groups of the oxidized base oils were pre-pared at diff...Inverse gas chromatographic technique(IGC) was attempted as a new approach to follow the chem-ical changes that occur during lubricating base oil oxidation.Three groups of the oxidized base oils were pre-pared at different oxygen flow rates,periods and temperatures according to IP48method.The corrected reten-tion volumes(VR) were calculated for a series of selected test solutes possessing different functional groups onthe oxidized base oils used as stationary phases.Kovats retention index(I),Flory-Huggins interaction parame-ter(κ1∞,2),and partial molar free energy of solution(ΔGL∞),were calculated for the given test solutes fromtheirVR.The relationships between theIvalues and the oxidation variables were plotted and discussed.Theobtained results were confirmed by potentiometric titration.The study reveals that the magnitudes of variationofI,κ1∞,2orΔG∞Lretention parameters depend on the oxidation degree of the base oil.Large differences be-tween theIvalues permit discrimination between the different oxidation steps.Key words: inverse gas chromatography(IGC);oxidation;lubricating base oil;Kovats retention展开更多
A novel integrated guidance and control (IGC) design method is proposed to solve problems of low control accuracy for a suicide unmanned combat aerial vehicle (UCAV) in the terminal attack stage. First of all, the IGC...A novel integrated guidance and control (IGC) design method is proposed to solve problems of low control accuracy for a suicide unmanned combat aerial vehicle (UCAV) in the terminal attack stage. First of all, the IGC system model of the UCAV is built based on the three-channel independent design idea, which reduces the difficulties of designing the controller. Then, IGC control laws are designed using the trajectory linearization control (TLC). A nonlinear disturbance observer (NDO) is introduced to the IGC controller to reject various uncertainties, such as the aerodynamic parameter perturbation and the measurement error interference. The stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the proposed IGC design method is verified in a terminal attack mission of the suicide UCAV. Finally, simulation results demonstrate the superiority and effectiveness in the aspects of guidance accuracy and system robustness.展开更多
Spindly calcium carbonate coated with AlOOH has been successfully prepared by bubbling carbonization method. SEM and XRD analysis results suggested an amorphous filiform the coating layer of AlOOH. Inverse gas chromat...Spindly calcium carbonate coated with AlOOH has been successfully prepared by bubbling carbonization method. SEM and XRD analysis results suggested an amorphous filiform the coating layer of AlOOH. Inverse gas chromatography (IGC) analysis indicated that γsD, the London component of surface energy of calcium carbonate increased after being coated with AlOOH, especially when with the coating weight quantity of 4%. And the reduction of the γsD value with the ascending column temperature became more obvious along with the increase of the coating weight quantity, which might be due to the desorption of water from the surface. In addition, the surface acid- alkali capacity of calcium carbonate also increased after coating.展开更多
A global fast convergent integrated guidance and control design approach is proposed. A disturbance observer is utilized to estimate the uncertainties of integrated guidance and control model in finite time. According...A global fast convergent integrated guidance and control design approach is proposed. A disturbance observer is utilized to estimate the uncertainties of integrated guidance and control model in finite time. According to the multiple sliding-mode surface control, the independent nonsingular terminal sliding functions are presented in each step, and all the sliding-mode surfaces run parallel. These presented sliding-mode surfaces keep zero value from a certain time, and the system states converge quickly in sliding phase. Therefore, the system response speed is increased. The proposed method offers the global convergent time analytically, which is useful to optimize the transient performance of system. Simulation results are used to verify the proposed method.展开更多
CaO formed by decomposing CaCO3 at 1450℃ was ground in a vibrational mill, then the long-time ground sample was reheated at different temperatures. Inverse Gas Chromatography (IGC) was used to measure the variation o...CaO formed by decomposing CaCO3 at 1450℃ was ground in a vibrational mill, then the long-time ground sample was reheated at different temperatures. Inverse Gas Chromatography (IGC) was used to measure the variation of the sample’s surface free energy under grinding and reheating. It is concluded that the total surface free energy and the London dispersive component of the surface free energy increases with grinding, while the polar component first increases with grinding, and then decreases , and finally disappears. When the long-time ground sample was reheated, its total surface free energy decreases , among which the London component decreases , but the polar component appears again.展开更多
In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimenta...In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimental results showed that the degree of alloying increased with the increase of ARB cycles and a supersaturatedα-Al solid solution accompanied with nanoprecipitates was formed in the Al-Mg alloys by ARB to 70 cycles.The as-prepared Al-Mg alloys exhibited enhanced mechanical properties,with a maximum tensile strength of∼615 MPa and a tensile elongation of∼10%at C_(Mg)=13 wt.%.The high strength can be attributed to different mechanisms,namely solid solution strengthening,grain boundary strengthening,dislocation strengthening,and precipitation strengthening.The Al-Mg alloys showed increased work hardening with increasing C_(Mg),due to the enhanced formation of nanoprecipitates.Meanwhile,no obvious drop in the intergranular corrosion(IGC)resistance was found in the Al-Mg alloys with C_(Mg) up to 13 wt.%.Moreover,sensitization treatment was found to induce little decrease in the IGC resistance of the Al-Mg alloys with C_(Mg)≤13 wt.%.We found that the excellent IGC resistance was due to the suppression of grain boundary precipitation by the preferred formation of precipitates within the grains that were induced by ARB.Our study indicated the novelty of the present solid-state alloying approach to achieving a superior combination of high mechanical properties and IGC resistance in Al-Mg alloys.展开更多
Owing to the importance of finding better methods and technologies for protecting against corrosion of aluminium alloys,research into the electrochemical characteristics of the corrosion is an ongoing concern.In this ...Owing to the importance of finding better methods and technologies for protecting against corrosion of aluminium alloys,research into the electrochemical characteristics of the corrosion is an ongoing concern.In this paper,the corrosion behaviour of Al-Mg-Si alloys in 3.5 wt% NaCl solution was investigated using multiple methods,including scanning electron microscopy(SEM),transmission electron microscopy(TEM),potentiodynamic polarisation measurement and electrochemical impedance spectroscopy(EIS).The results suggest that corrosion begins with dealloying of Mg,followed by conversion of MgSi particles into Al-Fe-Mn-Si particles.The corrosion rate increased until it reached a peak and then decreased.The increase in the corrosion rate may be attributed to an increased electrochemical driving force,which is produced by anodic dissolution between the matrix and residual MgSi particles.Additionally,the thin re-deposited layer of inert elements also plays an important role in accelerating the anodic process of the corrosion pit.The passivated corrosion pit and narrowed intergranular corrosion(IGC)pathway cause the area of active dissolution to decrease,thus reducing the corrosion rate.展开更多
文摘Inverse gas chromatographic technique(IGC) was attempted as a new approach to follow the chem-ical changes that occur during lubricating base oil oxidation.Three groups of the oxidized base oils were pre-pared at different oxygen flow rates,periods and temperatures according to IP48method.The corrected reten-tion volumes(VR) were calculated for a series of selected test solutes possessing different functional groups onthe oxidized base oils used as stationary phases.Kovats retention index(I),Flory-Huggins interaction parame-ter(κ1∞,2),and partial molar free energy of solution(ΔGL∞),were calculated for the given test solutes fromtheirVR.The relationships between theIvalues and the oxidation variables were plotted and discussed.Theobtained results were confirmed by potentiometric titration.The study reveals that the magnitudes of variationofI,κ1∞,2orΔG∞Lretention parameters depend on the oxidation degree of the base oil.Large differences be-tween theIvalues permit discrimination between the different oxidation steps.Key words: inverse gas chromatography(IGC);oxidation;lubricating base oil;Kovats retention
基金supported by the National Natural Science Foundation of China(6160150571501184)the National Aviation Science Foundation of China(20155196022)
文摘A novel integrated guidance and control (IGC) design method is proposed to solve problems of low control accuracy for a suicide unmanned combat aerial vehicle (UCAV) in the terminal attack stage. First of all, the IGC system model of the UCAV is built based on the three-channel independent design idea, which reduces the difficulties of designing the controller. Then, IGC control laws are designed using the trajectory linearization control (TLC). A nonlinear disturbance observer (NDO) is introduced to the IGC controller to reject various uncertainties, such as the aerodynamic parameter perturbation and the measurement error interference. The stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the proposed IGC design method is verified in a terminal attack mission of the suicide UCAV. Finally, simulation results demonstrate the superiority and effectiveness in the aspects of guidance accuracy and system robustness.
文摘Spindly calcium carbonate coated with AlOOH has been successfully prepared by bubbling carbonization method. SEM and XRD analysis results suggested an amorphous filiform the coating layer of AlOOH. Inverse gas chromatography (IGC) analysis indicated that γsD, the London component of surface energy of calcium carbonate increased after being coated with AlOOH, especially when with the coating weight quantity of 4%. And the reduction of the γsD value with the ascending column temperature became more obvious along with the increase of the coating weight quantity, which might be due to the desorption of water from the surface. In addition, the surface acid- alkali capacity of calcium carbonate also increased after coating.
基金Project(61673386)supported by the National Natural Science Foundation of ChinaProject(2018QNJJ006)supported by the High-Tech Institute of Xi’an,China
文摘A global fast convergent integrated guidance and control design approach is proposed. A disturbance observer is utilized to estimate the uncertainties of integrated guidance and control model in finite time. According to the multiple sliding-mode surface control, the independent nonsingular terminal sliding functions are presented in each step, and all the sliding-mode surfaces run parallel. These presented sliding-mode surfaces keep zero value from a certain time, and the system states converge quickly in sliding phase. Therefore, the system response speed is increased. The proposed method offers the global convergent time analytically, which is useful to optimize the transient performance of system. Simulation results are used to verify the proposed method.
基金Jointly funded by the National Excellent Young Scientists Foundation of China( No. 59925207) and the Natural Science Foun-dation of China (No.59872024)
文摘CaO formed by decomposing CaCO3 at 1450℃ was ground in a vibrational mill, then the long-time ground sample was reheated at different temperatures. Inverse Gas Chromatography (IGC) was used to measure the variation of the sample’s surface free energy under grinding and reheating. It is concluded that the total surface free energy and the London dispersive component of the surface free energy increases with grinding, while the polar component first increases with grinding, and then decreases , and finally disappears. When the long-time ground sample was reheated, its total surface free energy decreases , among which the London component decreases , but the polar component appears again.
基金supported by the National Natural Science Foundation of China(Nos.52175358 and 51371128)。
文摘In this study,a novel solid-state alloying approach was adopted to fabricate Al-Mg alloys with high Mg contents(C_(Mg)) by accumulative roll-bonding(ARB)of Al and Mg elemental materials to ultrahigh cycles.Experimental results showed that the degree of alloying increased with the increase of ARB cycles and a supersaturatedα-Al solid solution accompanied with nanoprecipitates was formed in the Al-Mg alloys by ARB to 70 cycles.The as-prepared Al-Mg alloys exhibited enhanced mechanical properties,with a maximum tensile strength of∼615 MPa and a tensile elongation of∼10%at C_(Mg)=13 wt.%.The high strength can be attributed to different mechanisms,namely solid solution strengthening,grain boundary strengthening,dislocation strengthening,and precipitation strengthening.The Al-Mg alloys showed increased work hardening with increasing C_(Mg),due to the enhanced formation of nanoprecipitates.Meanwhile,no obvious drop in the intergranular corrosion(IGC)resistance was found in the Al-Mg alloys with C_(Mg) up to 13 wt.%.Moreover,sensitization treatment was found to induce little decrease in the IGC resistance of the Al-Mg alloys with C_(Mg)≤13 wt.%.We found that the excellent IGC resistance was due to the suppression of grain boundary precipitation by the preferred formation of precipitates within the grains that were induced by ARB.Our study indicated the novelty of the present solid-state alloying approach to achieving a superior combination of high mechanical properties and IGC resistance in Al-Mg alloys.
基金financially supported by the Open Fund of Hunan Province Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle(No.KF1604)the National Defense Foundation of China(No.2011-006)。
文摘Owing to the importance of finding better methods and technologies for protecting against corrosion of aluminium alloys,research into the electrochemical characteristics of the corrosion is an ongoing concern.In this paper,the corrosion behaviour of Al-Mg-Si alloys in 3.5 wt% NaCl solution was investigated using multiple methods,including scanning electron microscopy(SEM),transmission electron microscopy(TEM),potentiodynamic polarisation measurement and electrochemical impedance spectroscopy(EIS).The results suggest that corrosion begins with dealloying of Mg,followed by conversion of MgSi particles into Al-Fe-Mn-Si particles.The corrosion rate increased until it reached a peak and then decreased.The increase in the corrosion rate may be attributed to an increased electrochemical driving force,which is produced by anodic dissolution between the matrix and residual MgSi particles.Additionally,the thin re-deposited layer of inert elements also plays an important role in accelerating the anodic process of the corrosion pit.The passivated corrosion pit and narrowed intergranular corrosion(IGC)pathway cause the area of active dissolution to decrease,thus reducing the corrosion rate.
