Controlled Synthesis of Silver Nanoparticles Using Double Reductants and Its Voltammetric Characteristics Study

Constructing robust silver nanoparticles (AgNPs) with good shape and dispersibility is of particular interest in analytical applications. Herein, monodispersibility AgNPs with the average size of 20 nm have been successfully prepared via one-pot method using sodium borohydride and trisodium citrate as co-reductants. The introduction of sodium borohydride greatly accelerated the rate of nucleation, which can effectively solve the problem of broad size distribution. Both shape and dispersibility of AgNPs can be effectively adjusted by simple control of refluxing time or concentrations of the sodium borohydride. We also studied the voltammetric characteristics of the AgNPs using Ag/AgCl solid-state voltammetry. An intense and stable current peak at a low potential could be obtained, which could provide a unique advantage in analytical applications. Copyright © 2016 BCREC GROUP. All rights reserved Received: 5th November 2015; Revised: 21st January 2016; Accepted: 22nd January 2016 How to Cite: Duan, Y., Xu, Z., Jiang, X. (2016). Controlled Synthesis of Silver Nanoparticles Using Double Reductants and Its Voltammetric Characteristics Study. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1): 115-119. (doi:10.9767/bcrec.11.1.433.115-119) Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.433.115-11

Magnetic Field Effects on Photocurrent and Photovoltaic Processes in Organic Solar Cells

Two mechanisms were investigated to understand the magnetic field effects on photocurrent (MFP), a phenomenon whereby an external magnetic field (MF) can increase or decrease photocurrent in organic solar cells (OSCs). The first one relates to MF-modulated intersystem crossing (ISC) between singlet and triplet polaron pairs and charge transfer (CT) complexes, accounting for the positive MFP in low and high magnetic field, respectively. The second mechanism originates from the interaction between triplet excited states and charge carriers, namely triplet-charge reaction (TCR). External magnetic field was found to reduce the rate constant of TCR, leading to negative MFP. MFP measurements were used to study the dissociation processes of singlet and triplet excitons in single-layer solar cells. It was found that the triplet excitons mainly dissociate directly into free charge carriers at the metal-electrode interface due to their long diffusion length, while the singlet excitons experience significant bulk dissociation into polaron pairs due to their short diffusion length. The interfacial dissociation of triplet excitons at the metal electrode can lead to enhanced photovoltaic (PV) response from phosphorescent materials as compared to the bulk dissociation of singlet excitons in fluorescent materials. measurements were also applied to study the charge carrier generation and recombination processes in bulk-heterojunction solar cells. It was found that dissociation of polaron pairs, triplet-charge reaction, dissociation of hot excitons, and photoinduced charge transfer are responsible for charge carrier generation in OSCs. High-field MFP reflects the recombination of dissociated electrons and holes towards the formation of singlet and triplet CT complexes in bulk-heterojunction OSCs. The annealing effect on the formation of CT complexes was also investigated. The PV efficiency of bulk-heterojunction solar cells was improved by uniformly dispersing phosphorescent heavy-metal complexes. The MFP results suggest that the spin-orbit coupling and the density of triplet excited states in conjugated polymer MEH-PPV were enhanced by external heavy-atom effect. The increased triplet density facilitated exciton dissociation and reduced charge recombination, and consequently improved the PV response in bulk-heterojunction cells

Comparative Study on Several Criteria for Non-equilibrium Phase Separation

Several different kinds of criteria for non-equilibrium phase separation to discriminate the two stages, the spinnodal decompostion (SD) and domain growth (DG), are compared and further investigated. The characteristic domain size and morphological function present two geometric criteria. Both of them can only provide rough estimations for the crossover from SD to DG. The reason for domain size is that the crossover in this description covers a process, instead of a specific time. The reason for the morphological function is that the result may rely on chosen threshold value. However, both the non-equilibrium strength and the entropy production rate are physical criteria and are more convenient to provide critical times. In fact, not only the non-equilibrium strength defined in the moment space opened by all the independent components of the used non-equilibrium quantities but also those defined in its subspaces can be used as criteria. Each of those criteria characterizes the phase separation process from its own perspective. Consequently, the obtained critical times may show slight differences. It should be pointed out that these slight differences are not contradictive, but consistent with each other and complementary in describing the complex phenomena.Comment: arXiv admin note: text overlap with arXiv:1808.0769

Social Media-Based Professional Development of Physical Education Teachers in China

In recent years, social media has played an important role in the professional development（PD）of physical education (PE) teachers (Jeffrey P. Carpenter & Stephen Harvey, 2020). There is a wealth of research on the professional development of PE teachers, but few relevant studies examined social media-based PDs. The purpose of this study was to specifically explore the research interests and changes in the PD of PE teachers in social media, and to explore the potential research space in this field. In this literature review, we followed three steps to conduct literature search. We used the following keywords: “social media”, OR “Wechat/Weibo”, AND “physical educators” or “PE teachers”, AND/OR “professional development” or “PD” for the literature search via the libraries resources of a large university in Shanghai, China. The search was limited to scholarly peer-reviewed journals. Then we cross-checked the bibliographies of the articles identified through direct library search to locate any missed articles. We next conducted direct searches in PubMed, Scilit, and ResearchGate with the same keywords. Inclusion criteria included: (a) the study must be from the perspective of social media; (b) the main results must involve teachers’ PD or related variables. A total of 56 highly relevant articles were retrieved and then saved to a data processing computer. The research team summarized and reported below several thematic findings. The main aspects of researches for social-media related PD of PE teachers were summarized including relevant concepts, connotation characteristics, theoretical basis, current development status, relevant factors, existing problems and corresponding strategies. The efficient communication and interaction as an important function of social media has attracted extensive attention and induced discussion in academic circles, where the topics mainly focus on the construction of identity, knowledge sharing, etc. Many related studies have continued examining the PD of individual teachers but are not specific to the reality of PE teacher groups, so the combination with the specific implementation of relevant theories on PE teacher groups needs more attention in related work. Social media can fill some of the gaps in PE teachers’ traditional PD community. It is necessary to conduct more comprehensive theoretical and empirical studies on social media-based PDs for PE teachers. The findings from this literature review shed light on the integration of resources needed to promote and thrive social media-based PD opportunities for PE teachers

A Review of Research on the Potential Value and Realistic Dilemma for Homework in Physical Education

Homework in physical education (PE) has become a central strategy of educational reform movements (Novak & Lynott, 2015). A Chinese policy called “the Double Reduction” provides an opportunity for the implementation of PE homework. There are abundant studies about homework in subjects like English, Math, Science, etc., but relatively few studies have been devoted specifically to PE homework. The primary purpose of this study was to analyze the value and dilemma of PE homework, with the goal of identifying the major contributions to the research knowledge base. We followed three parts to conduct the review: a) literature was searched using the following keywords: “PE homework”, OR “active homework”, AND “the value and dilemma”, AND/OR “homework in physical education” or “activity-based homework”; b) A document analysis was conducted regarding the Chinese policy related to homework in PE, including homework’s guidelines, composition system, and cultivation path, etc.; c) A total of 34 highly relevant articles were selected. The main value and dilemma of PE homework were summarized as follows: a) The PE homework appears to be an effective way of promoting policy implementation and renewal, providing a well-rounded approach to help students achieve educational goal, improving youth physical & mental health, and increasing communications with family members. b) The current PE homework has failed to realize the foregoing values due to some difficulties, including the lack of family exercise atmosphere, the absence of community organizations, and the huge amount of negative news in social media. c) Only three studies provided coping strategies to deal with the dilemma from a Social System Theory perspective, such as strengthening institutional construction, building a multivariate framework, shaping the paradigm, integrating online platform, and developing an assessment system. Most studies focused on the micro level about “the value and dilemma of homework implementation” without consideration of the other key factors from macro level. Based on the literature reviewed, a comprehensive theoretical model for PE homework is proposed to provide guidance for future research endeavors and facilitate implementation of the guidelines

FS_YOLOv8: A Deep Learning Network for Ground Fissures Instance Segmentation in UAV Images of the Coal Mining Area

The ground fissures caused by coal mining have seriously affected the ecological environment of the land. Timely and accurate identification and landfill treatment of ground fissures can avoid secondary geological disasters in coal mine areas. At present, the fissure identification methods based on deep learning show excellent performance on roads and walls, etc. Nevertheless, the automatic and reliable segmentation of ground fissures in remote sensing images poses a challenge for deep learning networks, due to the diverse and complex texture information included in the mining ground fissures and background. To overcome these challenges, we propose an improved YOLOv8 instance segmentation network to automatically and efficiently segment the ground fissures in coal mining areas. In detail, a model called FS_YOLOv8 is proposed. The DSPP (Dynamic Snake convolutional Pyramid Pooling) module is incorporated into the FS_YOLOv8 model to establish a multi-scale dynamic snake convolution feature aggregation structure. This module replaces the conventional convolution found in the SPPF module of YOLOv8 and aims to enhance the model's ability to extract features related to fissures with tubular structures. Furthermore, the D-LKA (Deformable Large Kernel Attention) module is employed to autonomously collect fissure context information. To enhance the detection capability of challenging samples in remote sensing images with intricate background and fissure texture, we employ a Slide Loss function. Ultimately, the ground fissure dataset of unmanned aerial vehicle (UAV) images in coal mine areas is subjected to experimental analysis. The experimental findings demonstrate that FS_YOLOv8 exhibits exceptional proficiency in segmenting ground fissures within intricate and expansive mining areas