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Tourist satisfaction, as a principal element for sustainable development of wetland ecotourism and destination competitiveness, has received extensive attention in the research on its impact on behavioral intention. This paper employs choice experiment to study tourist satisfaction as an important motivation for behavioral intention of willingness to pay and preference on wetland ecotourism improvement policy, and explores the potential causal mechanism. A 15-item scale is designed to measure tourist satisfaction and four constructs are defined. Under the framework of discrete choice modeling, unidimensional and multidimensional data are incorporated as the standard for population segmentation and explanatory variables. The empirical results estimated by three methods basically confirms the proposed hypotheses and indicate that tourist satisfaction has a certain effect on tourist preference of wetland ecotourism and there is significant preference heterogeneity among groups with different satisfaction. Besides, different dimensions of satisfaction have a different effect on tourist preference of wetland ecotourism. This study enriches the studies on non-market value evaluation and preference motivation in the field of ecotourism, because tourist satisfaction may explain some unobserved preference heterogeneity. More effective wetland ecotourism policies can be designed when data on satisfaction are included.

With the increasing attention and awareness of the ecological environment, ecotourism is becoming ever more popular, but it still brings problems and challenges to the sustainable development of the environment. To solve such challenges, it is necessary to review literature in the field of ecotourism and determine the key research issues and future research directions. This paper uses scientometrics implemented by CiteSpace to conduct an in-depth systematic review of research and development in the field of ecotourism. Two bibliographic datasets were obtained from the Web of Science, including a core dataset and an expanded dataset, containing articles published between 2003 and 2021. Our research shows that ecotourism has been developing rapidly in recent years. The research field of ecotourism spans many disciplines and is a comprehensive interdisciplinary subject. According to the research results, the evolution of ecotourism can be roughly divided into three phases: human disturbance, ecosystem services and sustainable development. It could be concluded that it has entered the third stage of Shneider's four-stage theory of scientific discipline. The research not only identifies the main clusters and their advance in ecotourism research based on high impact citations and research frontier formed by citations, but also presents readers with new insights through intuitive visual images.The online version contains supplementary material available at 10.1007/s10668-022-02190-0.

Rational control of the multiple emission outputs and achieving single-band and strong luminescence of Ln

New age smartphones are equipped with high processing power and internet connectivity. Hence, smartphones are capable of executing applications, which were only possible by desktops or laptops until recently. Some examples of such applications are email, banking, flight booking etc. People prefer to use mobile devices for these applications due to the usability and portability of mobile devices. However, because of hardware limitations, mobiles have limited resources such as battery life, power and capacity. Researchers are constantly looking for ways to maximize the usage of these resources. The execution of any application on mobile, needs storage capacity of mobile to store, battery life of mobile to keep running and processing capacity of mobile to process. Thus, more resources are needed to run more applications on these devices. To reduce the load of applications on mobile devices and use the resources efficiently, it is necessary to move some load of applications to remote cloud server in such a way that the applications will run seamlessly. Computation offloading for mobile-edge computing MEC) is a mechanism to utilize mobile resources well by moving resource-intensive applications to cloud server at network edge. In the case of multiple users, the total computing capacity of the server needs to be taken into consideration for allocating resources to multiple users. The key to efficient computation offloading is allocating applications to mobile and remote server in such a way that minimizes transmission energy. In this paper, we formulate the computation offloading problem as graph cut problem and propose a solution based on spectral clustering computation. First, for the applications on mobile a corresponding network flow graph model is defined. Then, label propagation theory is applied on the network graph and the network graph is simplified by compressing and combining. Finally, the optimal solution is obtained by computation using spectral clustering algorithm. Experiments show that the algorithm is effective in handling programs with loosely coupled as well as highly coupled functions.

To reduce data-storage costs and enhance high accuracy of industrial process fault detection, a data driven fault diagnosis method is proposed based on diffusion maps and hidden Markov model. Firstly, the correlation dimension of sample data is calculated. Secondly, the high-dimensional eigenvectors are extracted into low-dimensional manifold space by diffusion maps. Finally, the low-dimensional eigenvectors are regarded as the observation sequence of hidden Markov model for fault pattern recognition. The effectiveness of this new method is proved by TE process simulator. In addition, the fault identification results are demonstrated to be superior to the traditional identification approach of hidden Markov model.

Optical metamaterials (OMs) at visible wavelengths have been extensively developed. OMs reported recently are all composed of periodic structure, and fabricated by top-down approaches. Here demonstrated are the colored visible light frequency metamaterials composed of double layer array disordered and geometrical variational dendritic cells as well as fabricated by a novel bottom-up approach. The experiment demonstrates that the OMs composed of random silver dendritic cells caused the appearance of multiple transmission passbands at red and yellow light frequencies. Moreover, the slab focusing experiment reveals a clear point image in the range of half-wavelength with an intensity of 5 % higher than that of the light source. The proposed OMs will create a new way to prepare the cloak and the perfect lens suitable for optical frequency.

A 2.0 mm thick Al–Li alloy 2198-T8 plate is welded by friction stir welding in this work. Four dog-bone type samples are designed to use and measure stress–strain curves and mechanical properties. M(T) samples with transverse weld in the center are designed. Fatigue tests under different R ratio loads are performed on the welded samples with crack growing in the welded nugget and parent material samples. Fatigue crack growth rates in these welded nuggets are obtained and compared. It is shown that there is no peculiar yielding process in the stress–strain curve of the welded nugget compared with the parent material. Yield strength and tensile strength have a “U” shape through the weld zone and a lower value in the weld zone while the elongation is in reverse. Unlike the parent material, fatigue crack growth rates in the welded nugget are not sensitive to R ratios. Based on K res , finite element models are built and the crack closure method is used to calculate the effect of residual stress. Redistributions of residual stress with crack growth are taken into account. Fracture surfaces are investigated to summarize the fracture feature of the welded nugget under fatigue load.

Large-scale ordered ultralong silver nanobelts, which built a beautiful chrysanthemum-like structure, are prepared on the interface between dibutyl sebacate (DBS) and silver nitrate solution by a chemical electro-deposition technique. The influences of chemical circumvent of interface, concentration of silver nitrate solution and applied voltage on the formation of silver nanobelts are investigated. It is shown that the silver nanobelts possess a perfect single crystal structure and well-defined nanobelt-like morphology with a length of 5 mm, width 80–150 nm, and thickness 20 nm, respectively. The growth mechanism of the nanobelts is discussed. Furthermore, UV–vis spectra of the silver nanobelts show similar surface plasmon resonance properties to silver nanowires.

Left-handed metamaterials (LHMs) composed of random dendritic cells demonstrate a multi-band resonance and negative refractive index. A nano-assembly approach is established to fabricate optical LHMs. Random nanostructures of silver dendritic cells are prepared and further fabricated into a sandwich-like structure with a dielectric medium. The dentritic nano-assembled configuration reveals a multi-band resonance and a high intensity of the pass-band at infrared frequencies, and can be facilely and cheaply prepared on a large-scale of effective area.

Chlorophyll and xanthophyll were extracted from different plants for use as sensitizer colorants; cells were sensitized using chlorophyll, xanthophyll and a mixture of the two pigments. It was found that energy conversion efficiency ( η ) and maximum output power ( P max ) were 15.16% and 8.31% higher than that achieved by the linear superposition of the cells sensitized by individual pigments. This indicates that the mixed pigment co-sensitization entails a synergistic effect in the energy transfer of the pigment-sensitized mesoporous TiO 2 solar cells. Fluorescence analysis revealed that the electron transfer between chlorophyll and xanthophyll in the mixed pigment co-sensitized mesoporous TiO 2 solar cells was similar to that in ‘zigzag chains’ of photosynthesis.

This paper presents a centralized control system that coordinates parallel operations of power conditioning system (PCS) for battery energy storage system (BESS) in charge-discharge-storage power station. An overall energy management system is implemented to optimize power flow among different battery energy storage systems during both grid-connected and islanded operations. In islanded mode, the traditional load sharing strategy will result in battery aging and increased circulation if the state of charge (SOC) of each battery is different. Therefore, a power allocation strategy based on SOC and module capacity is designed, which can make full use of the total capacity of the parallel system. The design concept of the proposed centralized control system is evaluated through simulation and experiment studies under different test scenarios.

An unbalanced control strategy is proposed to eliminate the 2nd harmonic at the DC bus, based on a compound synchronous reference frame phase-locked loop (CSRF-PLL) system, which composed of a T/4 delay positive sequence PLL (PS-PLL) and a T/3&T/6 delay negative sequence PLL (NS-PLL). The proposed PLL system can detect the phase angle and frequency of the utility voltage without errors, and both of the positive-sequence and negative-sequence components in dq-coordinate system can be figured out concurrently. By interaction between the original signal and the delayed one, effect of some characteristic harmonics, e.g. −5th and +7th harmonics, will be obliterated. According to the principle of simultaneous power balance, a negative sequence current is injected into the positive sequence reference current via a negative-sequence-to-positive-sequence transformation (NS-PST). And a regulator composed of a PI link parallel with 2nd and 6th quasi-resonant links is designed. Finally, the simulation and experimental results demonstrate that the proposed PLL system can work well even when the input signals have severe asymmetry in both amplitude and phase angle, its advantage at handling with harmonics is verified as well. Furthermore, the unbalanced control strategy can suppress the 2nd harmonic at the DC port evidently, which would reduce the power loss and lengthen the cycle-life of the batteries installed in the power conditioning system (PCS).

An 18-pulse rectifier based on a step-up or step-down autotransformer in star-fork connection is presented. The voltage vector diagram of the autotransformer is given out and the connection of windings is also analyzed. By arrangement the secondly windings properly, the output voltage can be set in a wide range below or above the 3-phase uncontrolled rectifier with a low THD in the input current. Key analysis and results obtained via the Matlab simulation and some experimental results are presented for validation of the presented work.

This paper presents a physicals process hypothesis about the IGBT failure in according to the complex physical phenomena of IGBT burned when high-frequency arc-starting, after the analysis of pulse-transformer mathematical model and IGBT mathematical model, the corresponding simulation models are established, combining the specific experiments, the results show that the hypothesis is correct and reasonable, then a more reliable drive circuit is designed. It gives certain guiding significance to reliability design of plasma cutting power or other powers..

A method for the determination of trace amounts of water in high-purity silane, arsine and phosphine by gas chromatography (GC) is described. Samples are first passed through a transfer tube packed with calcium carbide to convert the water into acetylene, then through a liquid film packed column to eliminate the main hydride constituent. The analysis is performed by GC with flame-ionization detection. This method avoids contamination of the GC system.