Preparation and Mechanical Properties of Aligned Discontinuous Carbon Fiber Composites

Aligned discontinuous carbon fiber composites were fabricated from aligned discontinuous carbon fiber prepreg, which was prepared from continuous carbon fiber prepreg via mechanical high-frequency cutting. The internal quality and mechanical properties were characterized and compared with continuous carbon fiber composites. The results show that the internal quality of the aligned discontinuous carbon fiber composites is fine and the mechanical properties have high retention rate after the fibers were cut compared with continuous carbon fiber composites. The minimum retention rate of 0° tension strength is 63%, and the modulus is basically without chang. The minimum retention rates of 0° flexural strength and modulus are 85% and 78% respectively. The mechanical properties of aligned discontinuous carbon fiber composites are much better than that of the random oriented carbon fiber composites

Water Conservation Scenic Spots in China: Developing the Tourism Potential of Hydraulic Projects and Water Resources

The reservoir-related tourism industry has been developed for leisure purposes since the 1970s and has gained popularity worldwide. To promote reservoir-related tourism in China, the Chinese government launched a “top-down„ project titled “Water Conservation Scenic Spot„ (WCSS) in 2001. However, because of the lack of reasonable planning, innovative ideas, and effective governance, there are some problems with WCSS constraining its development. To deal with those problems, it is necessary to have a holistic understanding of the WCSS situation. This study analyses the origin, status, opportunities, and challenges of WCSS development in China. The results show a trend of periodic increase in the number of WCSSs between 2001 and 2016, and WCSS development is unbalanced regarding regions and types. Moreover, the main issues for the WCSS include the failure to follow WCSS guidelines in practice, weak awareness of the scientific educational function, monotonous planning and construction, a lack of cultural preservation, insufficient funding, weak marketing, damaging of natural resources, destruction of clusters of animals and plants, land surface erosion, and landscape pollution. These adverse effects can be alleviated by strengthening supervision and fostering balanced development, promoting education and protecting cultural resources, distributing funding and enlarging popularity, controlling the amount of tourism, and avoiding overexpansion. Overall, the findings of this study can encourage the development of WCSSs in the future and are of significance in supporting the reservoir-related tourism industry

Multilevel Rasch modeling of two-tier multiple choice test: A case study using Lawson’s classroom test of scientific reasoning

Assessment instruments composed of two-tier multiple choice (TTMC) items are widely used in science education as an effective method to evaluate students’ sophisticated understanding. In practice, however, there are often concerns regarding the common scoring methods of TTMC items, which include pair scoring and individual scoring schemes. The pair-scoring method is effective in suppressing “false positives” at the cost of missing possible middle states of progression of student understanding. On the other hand, the individual scoring method captures an undistinguished middle level but is prone to rewarding guessing, which leads to “false positives”. In addition, this middle level does not discriminate the progression between knowing the result and explaining the reason, which limits the capacity of drawing meaningful implications from the assessment outcomes. To address the concerns with the current scoring methods, it is valuable to explore new scoring method(s) that can fully utilize the information measured with TTMC items. In this study, a number of scoring models are studied using Rasch analysis on data of a popular TTMC test, the Lawson classroom test of scientific reasoning (LCTSR), collected from four considerably different populations. The results show that the model fit quality of the scoring methods varies with student population and item design. In general, there is no one-fits-all solution; however, given the new information obtained in this study, a three-step process is suggested that can guide the development of new mixed scoring models tailored for a particular population and or test. The evaluation results show that the mixed models produce the most reliable model fitting and better than average goodness of fit. Furthermore, the results in this study also confirm previous studies, which suggest that it is harder to come up with a correct explanation than to just know the answer

MLVCNN: Multi-Loop-View Convolutional Neural Network for 3D Shape Retrieval

3D shape retrieval has attracted much attention and become a hot topic in computer vision field recently.With the development of deep learning, 3D shape retrieval has also made great progress and many view-based methods have been introduced in recent years. However, how to represent 3D shapes better is still a challenging problem. At the same time, the intrinsic hierarchical associations among views still have not been well utilized. In order to tackle these problems, in this paper, we propose a multi-loop-view convolutional neural network (MLVCNN) framework for 3D shape retrieval. In this method, multiple groups of views are extracted from different loop directions first. Given these multiple loop views, the proposed MLVCNN framework introduces a hierarchical view-loop-shape architecture, i.e., the view level, the loop level, and the shape level, to conduct 3D shape representation from different scales. In the view-level, a convolutional neural network is first trained to extract view features. Then, the proposed Loop Normalization and LSTM are utilized for each loop of view to generate the loop-level features, which considering the intrinsic associations of the different views in the same loop. Finally, all the loop-level descriptors are combined into a shape-level descriptor for 3D shape representation, which is used for 3D shape retrieval. Our proposed method has been evaluated on the public 3D shape benchmark, i.e., ModelNet40. Experiments and comparisons with the state-of-the-art methods show that the proposed MLVCNN method can achieve significant performance improvement on 3D shape retrieval tasks. Our MLVCNN outperforms the state-of-the-art methods by the mAP of 4.84% in 3D shape retrieval task. We have also evaluated the performance of the proposed method on the 3D shape classification task where MLVCNN also achieves superior performance compared with recent methods

Squalene Monooxygenase Gene SsCI80130 Regulates Sporisorium scitamineum Mating/Filamentation and Pathogenicity

Sugarcane is an important sugar crop and energy crop worldwide. Sugarcane smut caused by Sporisorium scitamineum is a serious fungal disease that occurs worldwide, seriously affecting the yield and quality of sugarcane. It is essential to reveal the molecular pathogenesis of S. scitamineum to explore a new control strategy of sugarcane smut. Based on transcriptome sequencing data of two S. scitamineum strains Ss16 and Ss47, each with a different pathogenicity, our laboratory screened out the SsCI80130 gene predicted to encode squalene monooxygenase. In this study, we obtained the knockout mutants (ΔSs80130+ and ΔSs80130−) and complementary mutants (COM80130+ and COM80130−) of this gene by the polyethylene glycol-mediated (PEG-mediated) protoplast transformation technology, and then performed a functional analysis of the gene. The results showed that the deletion of the SsCI80130 gene resulted in the increased content of squalene (substrate for squalene monooxygenase) and decreased content of ergosterol (the final product of the ergosterol synthesis pathway) in S. scitamineum. Meanwhile, the sporidial growth rate of the knockout mutants was significantly slower than that of the wild type and complementary mutants; under cell-wall stress or oxidative stress, the growth of the knockout mutants was significantly inhibited. In addition, the sexual mating ability and pathogenicity of knockout mutants were significantly weakened, while the sexual mating ability could be restored by adding exogenous small-molecular signal substance cAMP (cyclic adenosine monophosphate) or tryptophol. It is speculated that the SsCI80130 gene was involved in the ergosterol biosynthesis in S. scitamineum and played an important role in the sporidial growth, stress response to different abiotic stresses (including cell wall stress and oxidative stress), sexual mating/filamentation and pathogenicity. Moreover, the SsCI80130 gene may affect the sexual mating and pathogenicity of S. scitamineum by regulating the ergosterol synthesis and the synthesis of the small-molecular signal substance cAMP or tryptophol required for sexual mating. This study reveals for the first time that the gene encoding squalene monooxygenase is involved in regulating the sexual mating and pathogenicity of S. scitamineum, providing a basis for the molecular pathogenic mechanism of S. scitamineum

Linking and comparing short and full-length concept inventories of electricity and magnetism using item response theory

In physics education research (PER), concept inventories (CIs) have become standard instruments for assessing students’ learning throughout instruction. To promote widespread use of concept inventories, previous studies have developed an approach to split a full length CI into short versions of CIs. This research extends the existing method to fully utilize the item response theory framework in equating and linking between the short CIs and the full length CIs. Three quantitative studies have been conducted: First, the extended algorithm is applied to divide the Brief Electricity and Magnetism Assessment (BEMA) into two half-length BEMAs (HBEMAs). Through a series of test-equating and validation analysis, the HBEMAs are confirmed to measure the same latent constructs of student understanding of electricity and magnetism to that of the original BEMA at a similar level of reliability. The second study establishes equivalent score conversions among the three versions of BEMA using the Stocking-Lord method, which has the best performance on equating error reduction among several methods explored. It is also confirmed that the equivalent statistical characteristics of the three versions of BEMA are equity and population invariant. In the third study, the extended algorithm is applied to link and compare the BEMA and the Conceptual Survey of Electricity and Magnetism (CSEM). After linking the BEMA and CSEM assessment scales, it becomes possible to directly convert and compare students’ performances on the two CIs. It is found that the scales of BEMA and CSEM are almost identical after scale transformation. Based on these studies, it can be suggested that all short and long versions of BEMA and CSEM can be used interchangeably after scale transformation

Net Anthropogenic Nitrogen Input and Its Relationship with Riverine Nitrogen Flux in a Typical Irrigated Area of China Based on an Improved NANI Budgeting Model

Excessive nitrogen (N) inputs from human activities in the watershed have resulted in water quality deterioration and other biological hazards. It is therefore critical to fully understand the anthropogenic N inputs and their potential impacts on regional water quality. In this study, a modified net anthropogenic nitrogen input (NANI) budgeting model considering the irrigation N input was developed and applied to investigate spatial–temporal variations of anthropogenic N inputs and their relationship with riverine N flux from 2005 to 2019 in a semi-arid irrigated watershed, Ulansuhai Nur watershed (UNW), China. The results showed that the annual average anthropogenic N inputs reached 14,048.0 kg N km−2 yr−1 without a significant temporal change trend. Chemical N fertilizer was the major contributor for watershed NANI and accounted for 75.3% of total NANI. Hotspots for N inputs were located in the central part of the watershed. In this study, watershed NANI does not have a significant regression relationship with riverine N export during the study period. Riverine N export showed an obvious decreased trend, which mainly was attributed to human activities. In addition, approximately 1.92% of NANI was delivered into the water body. Additionally, the N inputs into the watershed by the irrigation water accounted for 9.9% of total NANI. This study not only expands the application range of the NANI model in irrigated watersheds, but also provides useful information for watershed N management strategies

Effects of the Interlayer Toughening Agent Structure on the Flow Behavior during the z-RTM Process

In this paper, interlayer toughening composites were prepared by the z-directional injection RTM process (z-RTM), which has the advantage of increasing the interlaminar toughness and shortening the filling time and completely impregnating the fibers. The nonwoven fabrics and dot matrix structure material were used as ex situ interlayer toughening agents. The effect of the interlayer toughening agent structure on the resin flow behavior during the z-RTM process was investigated. The macro-flowing and micro-infiltration behaviors of the resin inside the preforms were deduced. The permeability of the fabric preforms with different toughening agents was investigated. The results show that the introduction of the nonwoven structure toughening agent makes the macro flow slow, and the flow front more uniform. The toughening agent with a dot matrix structure promotes the resin macro flow in the preforms, and shortens the injection time. The z-directional permeability of the preform with a dot matrix structural toughening agent is one order of magnitude lower than that of the non-toughened preform, while being higher than the preform toughened by the nonwoven fabric preforms, which is helpful for the further applicability of the z-RTM process. Furthermore, the mode II interlaminar fracture toughness of composites was evaluated

Consecutive Aromatic Carbon–Fluorine Bond and Carbon–Hydrogen Bond Activations by Iridium Porphyrins

Consecutive aromatic C–F bond and C–H bond activations of aryl fluorides were achieved by iridium porphyrins to initially give aryl and finally fluoroaryl iridium porphyrins. The C–F bond activation product is generated first, which is the precursor for the C–H bond activation. Both experimental and theoretical results support that the C–F bond is cleaved by iridium porphyrin anion through nucleophilic aromatic substitution, and the C–H bond cleavage is through homolytic aromatic substitution by iridium porphyrin radical followed by hydrogen atom abstraction. Moreover, the <i>meta</i>-fluorophenyl iridium porphyrin is the most thermodynamic stable regioisomers