To find out the distribution characteristics and influence of nutrients accumulated during aquaculture in freshwater ponds,three important freshwater aquaculture fishes in Shandong Province,including Cyprinus carpio(R1),Ctenopharyngoden idellus(R2)and Micropterus salmoides(R3)were selected and the nutrient status of overlying water,interstitial water and surface sediment of three ponds were monitored.The results showed that the concentrations of ammonia nitrogen,nitrite nitrogen,total nitrogen and total phosphorus of the overlying water in the aquaculture ponds were(0.781±0.047)mg/L,(0.123±0.005)mg/L,(5.059±0.060)mg/Land(0.317±0.011)mg/L,respectively,and most of them gradually increased with the aquaculture.And the concentration of total nitrogen during the aquaculture period and the concentrations of ammonia nitrogen and total phosphorus at the end of the experiment of the overlying water in R1 pond were significantly lower than those of R2 and R3.The concentrations of ammonia nitrogen,nitrite nitrogen,total nitrogen and total phosphorus of the interstitial water in different ponds were(5.273±0.177)mg/L,(0.188±0.006)mg/L,(11.368±0.386)mg/L and(1.372±0.042)mg/L,respectively,which were always higher than those in the overlying water.And the total nitrogen concentration of the interstitial water fluctuated and increased significantly.The concentrations of total nitrogen,total phosphorus and organic matter of sediments in different ponds were(0.489±0.010)％,(0.350± 0.005％)and(8.83±0.07)％,respectively.And the concentrations of total nitrogen sediment at the end of the experiment in all ponds were higher than those at the beginning of the experiment and those of R2 and R3 ponds increased significantly.The results of this study showed that the nitrogen and phosphorus nutrients of the aquaculture water and the total nitrogen of the sediment increased significantly during the aquaculture,and there were significant differences of the nutrient accumulation of the aquaculture water among different aquaculture fishes.Therefore,the feeding method should be formulated and timely adjusted according to the ecological habits of aquaculture organisms.In addition,the environmental conditions of aquaculture water body and sediment should be systematically and comprehensively considered,and the targeted control measures should be formulated scientifically according to the aquaculture species.
Enhancing public environmental awareness and behavior is the key to building an ecological civilization system,and it is also an effective way to achieve that clean waters and green mountains are like mountains of gold and silver.To explore the breadth of research fields related to environmental awareness and behavior,and explore important areas that have potential impact on their research in China,a visualization analysis was conducted using CiteSpace knowledge graph software on 278 relevant artides collected in the CNKI database of Chinese academic journals from 1998 to 2022,mainly including the charateristics of publication volume characteristics,journal source distribution,core author groups,hot topics,and frontier dynamics.It is found that research in this field has experienced four significant stages:the precursor period,the starting period,the development period,and the prosperity period.Research hotspots mainly focus on themes such as environmental awareness,environmental behavior,and environmental governance,while the frontier trends focus on three key areas:the relationship between environmental awareness and behavior,influencing factors,and the measurement of environmentally friendly behavior.Finally,it is suggested that in the future,three perspectives can be explored:building a comprehensive research system for environmental issues,deepening quantitative research on environmental awareness and behavior,and establishing a sound environmental friendly behavior scale to promote the in-depth development of research in the field of environmental awareness and behavior.
Poly oxometalates(POMs)are nanometer-sized metal oxide cluster compounds,which have attracted considerable attention in the fields of catalysis,medicine,surface science,and materials science owing to their nanosize and tunable acid/base,redox,magnetic,catalytic,and photochemical properties.In this study,supported by extensive experimental data,we conducted a detailed analysis of the enzyme-like properties of POMs,using Li7V15O36 as the proof-of-concept,and investigated their catalytic kinetics and mechanisms.Based on the principle that POMs can catalyze H2O2-based oxidation of peroxidase substrates 3,3',5,5'-tetramethylbenzidine to produce blue oxidation products,a simple,fast,sensitive,and selective colorimetric assay was proposed to detect glutathione.The linear range was found to be 1-80 µM,with a detection limit of 0.30 μ.M.Therefore,the developed glutathione sensing method based on POMs has great application potential in colorimetric detection field.
The purpose of this paper is to examine the mechanisms of different types of government support affecting firms'innovation output.Based on panel data of A-share listed companies from 2009 to 2017,a moderating mediating effect model is used to find that both government subsidies and R&D add-on deduction increase R&D investment and thus promote corporate innovation,with R&D add-on deduction having a better innovation incentive effect than government subsidies.Further analysis shows that the synergistic effects of different goverment support policies are different at different stages of the innouation process.The results of the sub-sample study show that government support policies are more effective in promoting R&D investment in state-owned enterprises,but more effective in improving innovation efficiency in non-state-owned enterprises.The synergistic effect of government support policies on firm innovation is more significant at higher levels of marketisation.The findings of this paper provide policy insights for government science and technology departments to make better use of the"combination of fiscal and tax policies"and improve government support to increase enterprises'R&D investment and thus promote substantive innovation.
At present,most existing image intelligent recognition methods exhibits large error because of too many distraction.Therefore,an intelligent image recognition method based on BF neural network is proposed.First,the static and dynamic image samples are collected by the sensor device,and then imported into an image acquisition card after passing through Bayer filters,which can decompose the image into three original colors in RGB mode.Second,the HOG feature is extracted to preprocess the image samples,and the forward propagation and backward propagation are respectively completed.Particularly,in the detection window of gray-scale image samples,the pixel gradient is calculated to further eliminate the interference of factors such as weakening light.The weight projection of the overlapping region is calculated,and the contrast is normalized,and finally the recognizable feature vector is obtained.The intelligent image recognition model based on BF neural network is constructed,in which the weight of the output layer and the hidden layer is adjusted by the gradient descent,and the ratio of positive and negative samples is 1∶3 for training.Comparative experiments are designed to test the feasibility of the proposed method.By comparing the proposed method with the BP neural network recognition method and the linear neural network recognition,it indicates that the recognition error of the proposed method is smaller than the results of the other two methods with different recognition times,which can effectively improve the accuracy of intelligent image recognition.
With the continuously deepening of globalization and the continuous advancement of industrialization and urbanization,the trend of continuously rapid expansion and growth of cities has begun to show unsustainable characteristics,especially under the influence of the COVID-19 pandemic and the drastic changes in the domestic and foreign social and economic environment.Some cities and regions in China have also begun to shrink.The chain problems caused by urban shrinkage began to hinder the further development of cities.This paper reviews the research progress of urban shrinkage at home and abroad from the aspects of phenomena,definitions,identification methods and types,causes and countermeasures.The research shows that urban shrinkage has global,regional,multi-dimensional and complex characteristics,but there is no unified analysis model.Firstly,the research framework system of urban shrinkage conforming to the law of urban development needs to be constructed scientifically.Secondly,the comprehensive and systematic research consistent with China's national conditions needs to be deepened.Thirdly,it is urgent to make countermeasures for urban shrinkage that adapt to the national conditions and meet the needs of future development.According to the research,it is necessary to further explore the concept and connotation of urban shrinkage and to reach a consensus on understanding.At the same time,the development of urban shrinkage theory should be guided by taking the advantages of multidisciplinary theories,and multi-scale comprehensive and in-depth research on urban shrinkage in different regions and with different types should be conducted by combining multi-source data and a variety of techniques.
In order to investigate the existence and uniqueness of almost anti-automorphic mild solutions of semi-linear differential equations,the concept of almost automorphic functions is first extended to almost anti-automorphic functions.Secondly,the related properties of almost anti-automorphic functions are discussed in this paper.It is proved that the set of all almost anti-automorphic functions constitutes a linear space with respect to the addition and multiplication of functions,which is given an infinite norm and then becomes a Banach space.Finally,by using the fixed point principle,the sufficient conditions for the existence and uniqueness of almost anti-automorphic mild solutions to a kind of semi-linear differential equations are obtained.Since the almost anti-automorphic function is more precise than the almost automorphic function,the discussion on the existence and uniqueness of the almost anti-automorphic mild solution of semi-linear differential equation can more accurately describe the dynamic properties of similinear differential equation than the discussion on the existence and uniqueness of the almost automorphic mild solution,the obtained conclusion is novel and serves as a further refinement and supplement to existing conclusions.
Artificial intelligence is the strategic commanding point of the new round of technological revolution and industrial competition,and the Chinese government has intensively introduced policies to support its high-quality and rapid development.By encoding the national policy texts on artificial intelligence in the past decade within the three-dimensional framework of"policy goals-policy issues-policy tools",it was found that the main goals of national policies on Artificial intelligence national policies are to build emerging industry patterns and technological innovation systems,lacking attention to the goals of improving infrastructure and cultivating high-end talents;Policy issues focus on industrial development and application,and gradually penetrate into various fields such as economy,society,national defense,ecology,etc.,showing a shift in the development direction of Artificial intelligence development,neglecting the development trend of basic research and technological research and development;In terms of policy tools,there is a phenomenon of supply based tools far exceeding demand based tools,and a positive interaction between supply based"push"and demand based"pull"has not been formed.Based on this,the article proposes suggestions to promote the healthy and sustainable development of artificial intelligence in China from the aspects of establishing an effective regulatory mechanism,clarifying strategic goals,enriching the use of policy tools,long-term support for basic research and development,improving the data ecosystem,and reflecting humanistic care.
This study aimed to explore the influence of low self-control on physical exercise and examine the mediating effects of sleep procrastination,negative emotions,and the moderating effect of trait mindfulness.A total of 1 416 university students were assessed using the Self-Control Scale,Physical Activity Level Scale,Sleep Procrastination Scale,Positive and Negative Affect Scale,and Trait Mindfulness Scale.The results indicate that:1)male university students exhibited significantly lower levels of sleep procrastination and negative emotions compared to female university students,while their physical exercise levels were significantly higher,and sleep procrastination increased significantly with grade level,and physical exercise levels decreased with grade level;2)low self-control(P＜0.001),sleep procrastination(P＜0.05),and negative emotions(P＜0.05)all negatively predicted physical exercise;3)there was a negative correlation between sleep procrastination and physical exercise(r=-0.066),but the direct predictive effect on physical exercise was not significant(P＞0.05);4)Sleep procrastination and negative emotions mediated the relationship between low self-control and physical exercise(P＜0.001).The study shows that:1)low self-control and negative emotions are barriers to physical exercise among university students;2)low self-control can directly impact the level of physical exercise among university students and can also induce sleep procrastination leading to negative emotions,which in turn disrupts physical exercise behavior;3)trait mindfulness significantly moderates the impact of low self-control on physical exercise among university students.
肥胖是体内白色脂肪组织过度积聚的状态,给肥胖者生理和心理健康均可造成负面影响.近年来我国儿童超重和肥胖率快速增加,已超过一些发达国家的水平.肥胖儿童体质偏低,更增加其成年后患肥胖相关疾病的风险,加重家庭和社会负担,严峻形势不容小觑.日常生活中过量摄入高油脂、高糖类等高热量饮食,"进大于出",膳食结构多样性减少加之睡眠和运动量不足是导致肥胖的主要外因.纠正这些不良生活习惯是防治肥胖的根本.本文从生命科学的角度,概述肥胖对儿童健康的危害,结合肥胖发生发展分子机制的研究进展,评述从源头上防治儿童肥胖的策略,希望为从事防治肥胖及相关疾病研究和关注后代健康的家庭,提供参考资料.
现代城市旅游形象的定位和传播是旅游高质量发展的重要条件.随着共享时代的到来在线旅游被更多旅游者接受,这种方式成为影响潜在旅游者形成旅游动机的重要来源.本文在梳理国内外旅游形象研究成果的基础上,以官方网站和网络游记为研究对象,利用Python网络爬虫技术和ROST CM6 软件对部分旅游城市进行网络文本分析,以成都市为例,对城市旅游形象感知进行研究,总结旅游形象与游客感知的异同,为准备改变旅游品牌的城市提供理论性的意见.
李之藻《同文算指》一书第十七部分"广诸乘方法"内容的来源问题在数学史界一直是个热门话题,已有研究指出其来自德国数学家施蒂菲尔《整数算术》一书第一章第五节的内容.这个结论存在明显问题,很值得商榷.为了解决这个问题,本文全面比较了上述两部分内容,并仔细分析了与之有关联的克拉维乌斯的《实用几何》一书.结果发现"广诸乘方法"的内容与《实用几何》第六章第十九节内容有很多地方相似,特别是在数据标注和书写形式方面,李之藻在编纂《同文算指》的时候应也部分收集或参照了《实用几何》中的一些内容.这一结果推进了关于《同文算指》和李之藻的相关研究,可为明末清初西方数学传入我国的相关研究提供参考.
从乡村振兴的视角,以产业、人才、文化、生态和组织五个维度构建城乡融合发展评价指标体系,运用熵值法、标准差、变异系数和地理探测器,分析2011-2020 年山东省城乡融合发展的时空演变特征及影响因素.结果表明:山东省城乡融合发展水平整体一般且空间差异显著,形成两核引领、双环环绕、区域联动的空间格局,呈现"中部高-南北低、沿海高-内陆低"的空间分异特征;2011-2020 年山东省城乡融合发展水平呈上升态势,但各地市发展差距不断增大,城乡融合发展"趋异"趋势明显,济南、青岛为城乡融合发展高水平区,滨州、菏泽及东营为低水平区.山东省城乡融合发展受社会保障、经济发展水平、城镇化水平、文教娱乐消费水平及信息化水平等多种因素的复合影响,其中,社会保障和经济发展水平是关键影响因子.
为进一步研究余暇体育锻炼氛围对大学生社交网络成瘾的影响,本文从认知重评和领悟社会支持之间的链式中介作用入手,探究其影响机制.通过问卷调查法、文献研究法和数理统计的方法,从余暇体育锻炼氛围、认知重评、领悟社会支持和社交网络成瘾四个方面对826 名大学生进行问卷调查.研究结果发现,认知重评和领悟社会支持在余暇体育锻炼氛围和社交网络成瘾之间存在链式中介作用,余暇体育锻炼氛围不仅直接影响社交网络成瘾,还能通过领悟社会支持和认知重评的链式中介作用间接影响社交网络成瘾.
党的二十大报告首次将教育、科技、人才三者统筹安排和一体部署,这是意义深远的重大创新.如果把三者理解为具有过程性质的教育实践、科技创性、人才工作,则对应三种不同的人才培养机制.文章通过比较研究三种人才培养机制在历史起源、关系演进、组织活动等三方面特征的异同,提出了三种人才培养机制在顶层设计、发展规律、价值取向、战略实施、规划编制等五个方面的协同育人机制,以期提高人才培养的系统性、科学性,为我国经济社会发展源源不断地培养大批优秀人才.
设In和Sn分别是有限集 Xn ={1,2,…,n}上的对称逆半群和对称群.对 0≤r≤n,令 I(n,r)={α∈In:∣im(α)∣≤r},则I(n,r)是对称逆半群In 的双边理想.对0≤r≤n － 1,再令In,r = Sn ∪I(n,r),则In,r 是对称逆半群In的子半群.为了研究半群In,r的极大(完全)独立子半群的完全分类,本文分析了半群In,r的格林关系及生成关系.首先,获得了半群In,r 的(完全)独立子半群的完全分类;其次,确定了半群In,r 的极大(完全)独立子半群的完全分类;最后,证明了半群In,r的极大独立子半群与极大完全独立子半群是一致的.
《财务会计》课程是高校经管类专业的主干核心课程之一.传统的财务会计教学滞后于实践,阻碍教学目标的实现.本文从《财务会计》课程的教学现状出发,以能力范式理念为指导,以学生学习产出为导向,在大智移云物区背景下分析《财务会计》教学过程中存在的诸如教学模式固化、教材内容滞后、理论实践"两张皮"、双师型教师占比低、教师团队建设不足、考核方式单一等方面的问题,提出开展以学生为中心的教学模式、丰富教学资源、加强理论与实践融合共进、增强师资力量、改革课程考核评价方式等教学改革的建议,使本课程的教学在应用型高校中真正达到能力范式下学生的人才培养目标要求.
为深入推进黄河流域生态保护和高质量发展,科学分析当前渔业发展形势,对"十三五"期间山东省黄河流域内 35 个县(市、区)的渔业产量、养殖面积、品种结构、苗种生产、从业人员、水产品加工、经济总产值进行了汇总分析,从养殖品种、产业结构、资源环境、基础设施方面剖析了当前流域内存在的主要问题,并相应提出了推动黄河流域渔业高质量发展的对策建议.
以北京地区的50 个常用月季品种为试验对象,研究了品种不同时间、地域间抗病性差异,分析不同月季品种影响月季黑斑病抗性的因素和黑斑病病症变化过程,进行了抗黑斑病的月季品种筛选.结果表明:月季黑斑病发病与气候有关,年度、月度发病率与降水量呈正相关,5 个不同抗性品种随生长情况表现出不同的适应性状表现.
我国盐碱地面积大,分布广,盐碱地由于含有大量盐离子不适合普通作物的生长.如何开发和利用好这些盐渍化土地对于解决我国的粮食和资源短缺问题至关重要.冰叶日中花是一种既耐干旱又耐盐碱的盐生植物,兼具食用价值和生态价值,在拓展盐渍化土地方面有很大的潜力.本文综述了冰叶日中花的耐盐机理并展望了其在盐碱地上的应用前景.
