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In the post-epidemic era, high-safety, low-density rural tourism projects have led to a period of rapid development, while the piecemeal land supply model has severely limited the development of rural tourism, resulting in the emergence of the "dotted layout, dotted land supply, dotted development" dotted land supply model. Since Zhejiang Province proposed the reform of "sloping villages and towns" in 2015 and carried out the exploration of dotted land supply, various regions have followed suit, formulated dotted land supply policies and launched rural tourism pilot projects according to local conditions, providing policy reference and practical experience for Wenzhou's dotted land supply reform. At present, there are still problems such as inadequate support from the higher law, poor adaptability of traditional control regulations, omissions in village regulations and deviations from expectations in project implementation.

InP/ZnS core/shell quantum dots have shown extraordinary application potential in photocatalysis. In this work, we demonstrated by ultrafast spectroscopy that the electron transfer ability of InP/ZnSe/ZnS core/shell/shell quantum dots was better than that of InP/ZnS quantum dots, because the introduction of ZnSe midshell resulted in improved passivation and greater exciton delocalization. The temperature-dependent PL spectra indicate that the exciton-phonon coupling strength and exciton binding energy of InP/ZnSe/ZnS quantum dots are smaller than those of InP/ZnS quantum dots. Further photocatalytic hydrogen evolution testing revealed that the photocatalytic activity of InP/ZnSe/ZnS quantum dots was significantly higher than that of InP/ZnS quantum dots, and InP/ZnSe/ZnS quantum dots even demonstrated improved stability. This research deepened our understanding of carrier dynamics and charge separation of InP/ZnSe/ZnS quantum dots, especially highlighting the application potential of InP/ZnSe/ZnS quantum dots in photocatalytic hydrogen evolution.

The current mountain tourism in Wenzhou suffers from lagging infrastructure construction, serious shortage of land for construction, lack of depth in tourism commodities and shortage of talents in the tourism industry. At the same time, the realistic and legal problems reflected in the touristic flow of mountainous hilly land resources are also hindering the further development of mountain tourism in Wenzhou. Based on this, it is proposed that the rights of mountainous land should be clarified, the regulations on tourism land should be improved, the supply mode of land should be innovated and the scientific guidance of the government should be strengthened.

A series of novel chiral pyridine-oxazolines were synthesized via catalytic asymmetric Heine reaction of meso-N-(2-picolinoyl)-aziridines.

A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of (2-alkylphenyl) ketones with benzosulfonimides is realized by a chiral N,N′-dioxide/NiII complex catalyst.

Prognostic of the proton-exchange membrane fuel cell can effectively extend the fuel cell lifespan, which can contribute to its large-scale commercialization. In this article, a hybrid prognostic approach is proposed to predict the fuel cell output voltage and other aging parameters that can reflect the stack’s internal degradation. During the training stage, the prognostic parameters are obtained by using the extended Kalman filter (EKF). Besides, the fuel cell output voltage is used to train the long short-term memory (LSTM) recurrent neural network. During the prediction stage, the hybrid EKF and LSTM method will predict the output voltage and aging parameters, and the degradation can be predicted under dynamic conditions. The proposed method is validated by experimental tests under static, quasi-dynamic, and dynamic conditions. Results indicate that the hybrid method can accurately predict the degradation trend of fuel cell voltage and aging parameters. The RMSE of the method is less than 0.0110, 0.0262, and 0.0317 under static, quasi-dynamic, and dynamic conditions, respectively, which are smaller than the conventional model-based methods or data-driven methods. Furthermore, the hybrid method can provide more detailed information for prognostic decision-making and better prolong the fuel cell lifespan.

The performance of the electromechanical actuator (EMA) in the aircraft braking system suffers from the system’s nonlinear characteristics, whereas the robust control can contribute to the improvement of tracking precision in its servo system. In this article, a chattering suppression fast terminal sliding mode (FTSM) control strategy with an embedded nonlinear disturbance observer (NDO) is proposed for the EMA braking system, which can retain the fast convergence characteristic of the classical FTSM and guarantee the system converges to equilibrium point timely. Moreover, the singularity problem of the classical FTSM control is resolved through the well-designed sliding mode manifold. The NDO is designed to estimate the uncertain factors online, including time-varying parameters, external disturbance, and unmolded dynamics of the EMA system. By applying the compensation terms into the control law, the proposed control strategy can alleviate the chattering problem and improve system stability. To verify the performance of the proposed control strategy for EMA, wheel braking tests are conducted under various conditions regarding the type of runway and failure cases. The results indicate that the proposed control strategy can guarantee the servo performance, the control precision, and the response speed of the EMA servo system.

Nonlinear optical limiting (OL) properties of carboxyl-functionalized Ti

A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of

An asymmetric organocatalytic nucleophilic aromatic substitution reaction of azlactones with electron-deficient aryls was established. A variety of α-aryl α-alkyl α-amino acid esters and peptides were obtained in decent yields and stereoselectivities. A new bifunctional catalytic mode involving charge-transfer interaction and hydrogen bonding is proposed to explain the enantioselectivity.

The nonlinear absorption effect in a Fe-porphyrin metal-organic framework (Co-TCPP(Fe) MOF) was studied using the nanosecond Z-scan technique, which showed an enhanced reverse saturation absorption (RSA) compared with TCPP(Fe) ligand. By femtosecond transient absorption (fs-TA) measurements, the charge transfer dynamics of MOF are unveiled. Compared with TCPP(Fe) ligand, the ultrafast formation of charge separation states (CSSs) with extra-long lifetime (> 3.5 ns) detracts the recombination of electron-hole pairs, resulting in an enhanced excited state absorption (ESA). Based on the strong ESA caused by CSSs absorption, the MOF nanosheets showed an excellent optical limiting (OL) effect with the OL threshold of 0.89 J/cm2.

Utilization of triplet excitons, which generally emit poorly, is always fundamental to realize highly efficient organic light-emitting diodes (LEDs). While triplet harvest and energy transfer via electron exchange between triplet donor and acceptor are fully understood in doped organic phosphorescence and delayed fluorescence systems, the utilization and energy transfer of triplet excitons in quasi-two-dimensional (quasi-2D) perovskite are still ambiguous. Here, we use an orange-phosphorescence-emitting ultrathin organic layer to probe triplet behavior in the sky-blue-emitting quasi-2D perovskite. The delicate white LEDs architecture enables a carefully tailored Dexter-like energy-transfer mode that largely rescues the triplet excitons in quasi-2D perovskite. Our white organic-inorganic LEDs achieve maximum forward-viewing external quantum efficiency of 8.6% and luminance over 15000 cd m-2, exhibiting a significant efficiency enhancement versus the corresponding sky-blue perovskite LED (4.6%). The efficient management of energy transfer between excitons in quasi-2D perovskite and Frenkel excitons in organic layer opens the door to fully utilizing excitons for white organic-inorganic LEDs.

English education has been promoted widely in China and has driven scholarly attention to young Chinese learners of English. However, not much has been done to address language ideologies embedded ...

Polymer crystalsomes are a class of hollow crystalline polymer nanoparticles with shells formed by single crystals with broken translational symmetry. They have shown intriguing mechanical, thermal, and biomedical properties associated with spherical packing. Previously reported crystalsomes are formed by quasi-2D lamellae which can readily tile on a spherical surface. In this work, the formation of polymer crystalsomes formed by 1D polymer crystals is reported. Poly (3-hexylthiophene) (P3HT) is chosen as the model polymer because of its 1D growth habit. P3HT crystalsomes are successfully fabricated using a miniemulsion solution crystallization method, as confirmed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction (XRD) and selected area electron diffraction experiments confirm that P3HT crystallized into a Form I crystal structure. XRD, differential scanning calorimetry and UV-Vis results reveal curvature-dependent structural, thermal and electro-optical properties.

The power converters can play an important role in fuel cell systems, and robust control design of the converters can improve both the system efficiency and stability. In this paper, an advanced control strategy of a two-phase interleaved boost converter for fuel cell applications is proposed and implemented, which consists of the outer voltage regulation loop and the inner current tracking loop. The current inner loop is designed based on the Super-Twisting sliding mode control to track its reference current tightly. The active disturbance rejection control (ADRC) is applied to the voltage outer loop to regulate the output voltage and generate the reference current for the inner loop. The stability of the control loops is proved through the Lyapunov stability theory and Routh-Hurwitz criteria. Finally, the effectiveness of the proposed control strategy is demonstrated by numerical simulation results, which indicates that strong robustness can be achieved when compared with traditional dual-loop PI controller.

The nonlinear optical limiting (OL) property of tin phthalocyanine porous organic frameworks (Sn-Pc-POFs) dispersion in the nanosecond regime was studied, which showed excellent dispersibility and stability as well as a low OL threshold. To clarify the nonlinear optical response mechanisms in the material, the energy level structure of Sn-Pc-POFs was simulated using the density functional theory calculation, and the photoinduced carrier dynamics was studied using femtosecond time-resolved transient absorption spectroscopy. The results indicated that the large absorption cross section and long lifetime of the excited state were responsible for the excellent OL property of the material.

The bidirectional DC-DC converter is widely used in continuous power supply, hybrid vehicles, and battery charging. In this paper, a bidirectional quadratic boost-buck with wide input voltage range and high conversion ratio is studied. A sliding mode controller (SMC) with fixed frequency is designed. The simulation verification was conducted in the Matlab/Simulink environment. and the comparison analysis was conducted with PI algorithm. Finally, a prototype is implemented to verify the simulation. Simulation and experimental results show that the converter with sliding mode control has strong robustness and good dynamic quality under large disturbance of load and line voltage.

Two-dimensional Ti3C2Tx nanosheets have drawn much attention due to their unique nonlinear optical properties. To enhance the optical nonlinearity of the material, we synthesized Ti3C2Tx composites decorated with silver nanoparticles (Ti3C2Tx/Ag) through self-assembling of Ag nanoparticles on the surface of Ti3C2Tx. The nonlinear optical properties the composite were studied via nanosecond laser Z-scan method, and enhanced saturable absorption (SA) and reversed saturable absorption (RSA) effects were demonstrated. Using the femtosecond time-resolved transient absorption measurements, the carrier dynamics in the nonlinear response, as well as the enhancement mechanism of the composites was clarified.

The existing controller can hardly guarantee the operating stability of aircraft anti-skid braking system. To overcome the higher order nonlinearity and parameters variability of large passenger aircraft with electro-hydrostatic actuator (EHA) anti-skid braking system, a dynamic surface control approach, which based on barrier Lyapunov function (BLF), is proposed to design a slip ratio tracking control with an upper constraint. The purpose of the proposed BLF is to prevent constraint violation to ensure stability. A whole state space model of EHA anti-skid braking system is developed and simplified reasonably to a strict feedback form, whose model uncertainties are considered as unknown external disturbances. A nonlinear disturbance observer (NDO) is utilized to compensate this external disturbance. Through Lyapunov stability analysis, it is noticed that the proposed control strategy can converge to a small neighborhood of the origin by appropriately adjusting the controller parameters. Moreover, it can guarantee the tracking error is with semiglobal, uniform, and ultimate bounded. By using the employed control algorithm, the proposed controller enhanced braking performance and safety, which ensures the closed-loop system operating in the stable region of the friction curve. The proposed method eliminated the explosion problem of terms existing in traditional back-stepping approach and was easier to be implemented. The performance and the effectiveness of the proposed controller have been verified by carrying out simulation and real-time Hardware-in-Loop experiment.

In this paper an adaptive non-singular fast terminal sliding mode (NFTSM) control scheme is proposed to control the electro-mechanical actuator (EMA) in an electric braking system which is a complex electro-mechanical system. In order to realize high-performance brake pressure servo control, a radial basis function (RBF) neural network method is adopted to deal with the difficulty of estimating the upper bound of the compound disturbance in the system, to reduce the conservatism of the design of sliding mode switching gain, and effectively eliminate sliding mode chattering. The simulation results show that, compared with a linear controller, the proposed control strategy is able to improve the servo performance and control precision. In addition the response speed of the braking actuator is enhanced significantly, without changing the traditional double-loop control structure.

Focus on the ripple of the output voltage of switched reluctance generator (SRG), an optimized controller of turn-on and turn-off angle basing on fuzzy logic is designed. The effect of turn-on and turn-off angle on system's performance is studied after introducing the working principle of SRG. Considering the ripple of output voltage and the difference between the real voltage and the reference voltage, the voltage of SRG is limited near the reference voltage by optimizing the turn-on and turn-off angle through fuzzy logic method. The self-exciting SRG model which adopts voltage feedback control is built to validate this controller's correctness and robustness. Compared with traditional PI control method, the fuzzy logic algorithm can restrain the voltage ripple and strengthen system's static performance well.

Chemical absorption of CO 2 is deemed as an effectively controllable way to accomplish large reduction of greenhouse gas emission. A two dimensional (2-D) model for two-phase flows is established for chemical absorption of CO 2 in the packed column. A good agreement has been reached between the simulated temperature and fluid flow profiles and experimental results. The field synergy equations are deduced to optimize the fluid flow, mass transfer, heat transfer and chemical reaction by an established Lagrange function. The synergy angle is an index to express the synergy degree among the physical phenomena. The global field synergy optimized velocity field, temperature distribution and gas concentration variation trend are obtained, contributing to improvement of 9% CO 2 removal efficiency. Meanwhile, the entropy generation rate was well applied to quantify the overall improvement from the perspective of exergy. The results indicated that the entropy generation rate induced by mass transfer and reaction composes the most part of the irreversibility. The exergy loss is reduced by 12.8% after global field synergy optimization mainly for the two resistances reduction. The results showed that the field synergy optimization could be an intensification method for CO 2 capture, whose improvement effect could be assessed by entropy generation analysis.

With the fast development of the society, the amount of carbon dioxide has been increased enormously in the atmosphere all over the world, which has already endangered the survival of human being. More and more people or organizations are studying new technologies to reduce the cost of capturing CO2. The recovery and sequestration of CO2 from flue gas of the power plant is regarded as a feasible way to mitigate the greenhouse gas emissions. Therefore, the process of recovering carbon dioxide by chemical absorption with monoethanolamine (MEA) in industry was emphatically described in this paper. Based on energy integration, a coupled process was proposed which included MEA absorption of CO2 and SO2, and the heat recovery from the flue gas’s waste heat recovery unit and compressor inter-stage cooling unit. Compared the innovative process with an original process, 9% of thermal energy could be reduced in the new flowsheet. Meanwhile decarbonization and desulphurization could be carried on in the absorber simultaneously without the usual wet flue gas desulphurization (FGD) system. An exergy analysis model was established and validated by the literature data with a deviation less than 5.40%. The exergy results indicated that the exergy loss of the improved process was 15.48–20.75% less than that of the original one, which proved that the innovative process was reasonable and effective from the perspective of energy utilization.

A high order sliding mode control (HOSMC) algorithm is proposed to control the nonlinear system with parameter uncertainty in this paper, with the purpose of the chattering avoidance. According to the aircraft antiskid braking system(ABS) model, a HOSMC algorithm is presented and a bipolar sigmoid function is developed. The stability and convergence of proposed algorithm is analyzed with Lyapunov theory in finite time. The results indicate that the HOSMC algorithm has a better performance and chattering avoidance than the conditional ones. Additionally the maximum friction coefficient is acquired in a short time, and the optimal slip ratio is achieved under the runway simulation. KEYWORD: high order sliding mode; slip ratio; anti-skid braking system; aircraft