Search

Urban national parks (UNPs) provide tourism services in cities worldwide. However, the factors affecting tourist distributions in UNP activity and path spaces remain uncertain. Using Web crawler technology, location big data were tracked and sampled in Donghu National Park in Wuhan, China, and 12 predictor variables were analyzed using a machine-learning method (i.e., random forest). The consistency of the big data compared to the population census and tourist observations was determined at 79.5% and 77.8%, respectively. The tourist number (p) and tourist density (p/ha) per day in the park space in Donghu National Park were 0–2,531 p and 0–198.0 p/ha, respectively. Peak tourist periods showed pressure flows of 0.3–34.5‰ between scenic areas in the park. An analytical framework was formulated for UNPs to link the urban environment, park attributes, and configurational attributes, which here explained 66.4%–72.5% of the tourist distribution in the path and activity spaces. Random forest models performed better than geographically weighted regression (GWR) or ordinary least squares (OLS) models, indicating a complex nonlinear relationship between the independent variables and tourist distribution in UNP spaces, rather than the linear relationship that has previously been found in urban parks. First, both activity and path spaces near developed urban environments or park entrances bore higher tourism pressure. Second, winding routes attracted tourists to path spaces, while water landscapes attracted tourists to both path and activity spaces. Third, tourism pressure in path spaces was determined by configurational attributes. These results are important reference points for the planning and management of UNPs. [ABSTRACT FROM AUTHOR]

The fast convergence without initial value dependence is the key to solving large angle relative orientation. Therefore, a hybrid conjugate gradient algorithm is proposed in this paper. The concrete process is: ① stochastic hill climbing(SHC) algorithm is used to make a random disturbance to the given initial value of the relative orientation element, and the new value to guarantee the optimization direction is generated. ②In local optimization, a super-linear convergent conjugate gradient method is used to replace the steepest descent method in relative orientation to improve its convergence rate. ③The global convergence condition is that the calculation error is less than the prescribed limit error. The comparison experiment shows that the method proposed in this paper is independent of the initial value, and has higher accuracy and fewer iterations.

Nanosized CdS/polymer composite fiber mats were fabricated via a facile electrospinning processing, and the as-prepared composite fiber mats showed excellent photodegradation ability to methylene blue (MB). Polymers bearing N and S atoms with affinity to Cd2+ ions were first synthesized and then used to prepare CdS/polymer composite fibers. In this work, coaxial electrospinning was employed to achieve the preparation of the desired composite fibers using special polymers as core and cadmium acetate [Cd(CH3COO)2] as shell. Then, fiber mats were immersed in thioacetamide (TAA) solution for several minutes, and CdS/polymer composite mats were obtained eventually. The photodegradation catalytic ability was tested using MB as a model dye under sunlight. The photocatalytic efficiency of the CdS/polymer composite fiber mat was recorded and studied by UV-visible spectra, and it showed high efficiency. Nanofiber mats will find real applications in the treatment of wastewater. [ABSTRACT FROM AUTHOR]

TiO2/ PVA composite nanofiber mat was prepared via an electrospinning technology. SH-TiO2-SiO2 hybrid particles and PVA solution were injected through a coaxial syringe, yielding a composite nanofiber mat. The as-prepared SH-TiO2-SiO2/ PVA composite nanofiber mat was immersed in Cd2+ cation solution and S2− anion solution in turn. Thus, yellow TiO2@CdS/ PVA composite nanofiber mats were prepared. By adjusting the number of times a mat was immersed in the Cd2+ and S2− solutions, different amounts of CdS particles attaching to the mats were obtained. Both SH-TiO2-SiO2/ PVA and TiO2@CdS/ PVA composite nanofiber mats were employed to catalyze the photodegradation of a model dye, methylene blue. The photodegradation performance could be greatly enhanced by the introduction of CdS particles anchoring onto TiO2 particles. The photodegradation efficiency reached 99.2% within 180 min. Also, the nanofiber mat could be recycled and reused at least 10 times. The photodegradation efficiency of TiO2@CdS/ PVA composite nanofiber mats remained 68.8% for 10 cycles. [ABSTRACT FROM AUTHOR]

Three small molecular boron dipyrromethene (BODIPY) derivatives (B3a, B3b and B3c) were well-designed and synthesized at first, and then were incorporated into polyurethane to obtain macromolecular fluorescent sensors. These small molecular BODIPY derivatives exhibited high sensitivity and selectivity to Hg 2 + , Cr 3 + and Fe 3 + ions. The colors of these chemicals changed rapidly upon the addition of Hg 2 + , Cr 3 + and Fe 3 + ions. In addition, their fluorescence peaks shifted and was enhanced as well. B3a, B3b and B3c still remained the sensing properties when being introduced to polyurethane (PU). The functionalized PU films not only showed color change and fluorescence shift for detecting Hg 2 + , Cr 3 + and Fe 3 + ions as their small molecular counterparts, but also triggered a new emission peak in 500–600 nm. Besides, the functionalized PU film (PU-B3a as a sample) could absorb Hg 2 + ions more than 84 mg/g in unit time and volume. It suggested that as long as the structure of the small molecular sensor was remained, the fluorescent ability remained even it is introduced to the macromolecular chains. In addition, Glass transition temperature (T g ) of the PU films changed when B3a, B3b and B3c were introduced. [ABSTRACT FROM AUTHOR]