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做有心人,做素心人——蔡鸿生先生《学境》读后
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作者 殷小平 曾玲玲 《学术研究》 CSSCI 北大核心 2002年第6期126-128,共3页
蔡鸿生先生的《学境》一书,终于出版了。(香港博士苑出版社,2001年12月)由于负责校对的机缘,我们得以提前拜读。蔡先生在序引中指出:“学术境界,说到底是一个精神境界的问题。”对于这样一个玄之又玄的问题,蔡先生深知“只可意会... 蔡鸿生先生的《学境》一书,终于出版了。(香港博士苑出版社,2001年12月)由于负责校对的机缘,我们得以提前拜读。蔡先生在序引中指出:“学术境界,说到底是一个精神境界的问题。”对于这样一个玄之又玄的问题,蔡先生深知“只可意会而不可言传”,但仍有“心法”可为后学指明。该书收录的30篇文章,除…… 展开更多
关键词 蔡鸿生 《学境》 评价
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做有心人,做素心人——蔡鸿生先生《学境》读后
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作者 殷小平 曾玲玲 《中山大学研究生学刊(社会科学版)》 2001年第4期68-72,共5页
本文对蔡鸿生先生所著《学境》一书作了简要评述,并围绕其主旨,结合自身的学习体会,着重从读书与治学两个方面出发,提倡在校学生应端正学习态度,树立严谨的治学风气。
关键词 蔡鸿生 《学境》 习态度 青年
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Lecturers’Efforts in Building Rapport in the English-Medium Instruction(EMI)Context:Focus on the Use of Communication Strategies
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作者 Shiyan YU Jagdish KAUR 《Chinese Journal of Applied Linguistics》 2024年第3期498-513,526,共17页
Past studies reveal the prevalence of anxiety,coupled with low motivation and disengagement among students in English-medium instruction(EMI)programs.Given the detrimental impact these negative emotions can have on le... Past studies reveal the prevalence of anxiety,coupled with low motivation and disengagement among students in English-medium instruction(EMI)programs.Given the detrimental impact these negative emotions can have on learning outcomes,it is imperative that teachers establish positive emotional rapport with their students.This study explores how experienced and highly rated EMI lecturers at a Chinese university’s overseas campus use communication strategies to build rapport with their students during interactive academic activities.It identifies the strategies used by these lecturers and examines how the strategies facilitate the teaching-learning process.The data,consisting of 10 hours of tutorials and 10 hours of supervisor-student supervision meetings,is analyzed using an adapted Conversation Analysis(CA)approach.The analysis reveals three types of communication strategies(CSs)frequently used by lecturers:back-channeling,codeswitching,and co-creation of messages.By employing these strategies,the lecturers established a strong rapport with the students,which created an encouraging and supportive learning environment.Consequently,this positive atmosphere facilitated students’learning of content knowledge through English.The findings of this study have implications for the training of lecturers who encounter difficulties in establishing rapport with multilingual students in the EMI setting. 展开更多
关键词 communication strategies English-medium instruction(EMI) rapport-building lecturer-student interaction supportive learning environment
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Tomato detection method using domain adaptive learning for dense planting environments
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作者 LI Yang HOU Wenhui +4 位作者 YANG Huihuang RAO Yuan WANG Tan JIN Xiu ZHU Jun 《农业工程学报》 EI CAS CSCD 北大核心 2024年第13期134-145,共12页
This study aimed to address the challenge of accurately and reliably detecting tomatoes in dense planting environments,a critical prerequisite for the automation implementation of robotic harvesting.However,the heavy ... This study aimed to address the challenge of accurately and reliably detecting tomatoes in dense planting environments,a critical prerequisite for the automation implementation of robotic harvesting.However,the heavy reliance on extensive manually annotated datasets for training deep learning models still poses significant limitations to their application in real-world agricultural production environments.To overcome these limitations,we employed domain adaptive learning approach combined with the YOLOv5 model to develop a novel tomato detection model called as TDA-YOLO(tomato detection domain adaptation).We designated the normal illumination scenes in dense planting environments as the source domain and utilized various other illumination scenes as the target domain.To construct bridge mechanism between source and target domains,neural preset for color style transfer is introduced to generate a pseudo-dataset,which served to deal with domain discrepancy.Furthermore,this study combines the semi-supervised learning method to enable the model to extract domain-invariant features more fully,and uses knowledge distillation to improve the model's ability to adapt to the target domain.Additionally,for purpose of promoting inference speed and low computational demand,the lightweight FasterNet network was integrated into the YOLOv5's C3 module,creating a modified C3_Faster module.The experimental results demonstrated that the proposed TDA-YOLO model significantly outperformed original YOLOv5s model,achieving a mAP(mean average precision)of 96.80%for tomato detection across diverse scenarios in dense planting environments,increasing by 7.19 percentage points;Compared with the latest YOLOv8 and YOLOv9,it is also 2.17 and 1.19 percentage points higher,respectively.The model's average detection time per image was an impressive 15 milliseconds,with a FLOPs(floating point operations per second)count of 13.8 G.After acceleration processing,the detection accuracy of the TDA-YOLO model on the Jetson Xavier NX development board is 90.95%,the mAP value is 91.35%,and the detection time of each image is 21 ms,which can still meet the requirements of real-time detection of tomatoes in dense planting environment.The experimental results show that the proposed TDA-YOLO model can accurately and quickly detect tomatoes in dense planting environment,and at the same time avoid the use of a large number of annotated data,which provides technical support for the development of automatic harvesting systems for tomatoes and other fruits. 展开更多
关键词 PLANTS MODELS domain adaptive tomato detection illumination variation semi-supervised learning dense planting environments
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Prognositic value of anoikis and tumor immune microenvironment-related gene in the treatment of osteosarcoma
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作者 WANG Dong DENG Qing +7 位作者 PENG Yi TONG Zhaochen LI Zixin HUANG Liping ZENG Jin LI Jinsong MIAO Jinglei CHEN Shijie 《中南大学学报(医学版)》 CAS CSCD 北大核心 2024年第5期758-774,共17页
Objective:Osteosarcoma is a highly aggressive primary malignant bone tumor commonly seen in children and adolescents,with a poor prognosis.Anchorage-dependent cell death(anoikis)has been proven to be indispensable in ... Objective:Osteosarcoma is a highly aggressive primary malignant bone tumor commonly seen in children and adolescents,with a poor prognosis.Anchorage-dependent cell death(anoikis)has been proven to be indispensable in tumor metastasis,regulating the migration and adhesion of tumor cells at the primary site.However,as a type of programmed cell death,anoikis is rarely studied in osteosarcoma,especially in the tumor immune microenvironment.This study aims to clarify prognostic value of anoikis and tumor immune microenvironment-related gene in the treatment of osteosarcoma.Methods:Anoikis-related genes(ANRGs)were obtained from GeneCards.Clinical information and ANRGs expression profiles of osteosarcoma patients were sourced from the therapeutically applicable research to generate effective therapies and Gene Expression Omnibus(GEO)databases.ANRGs highly associated with tumor immune microenvironment were identified by the estimate package and the weighted gene coexpression network analysis(WGCNA)algorithm.Machine learning algorithms were performed to construct long-term survival predictive strategy,each sample was divided into high-risk and low-risk subgroups,which was further verified in the GEO cohort.Finally,based on single-cell RNA-seq from the GEO database,analysis was done on the function of signature genes in the osteosarcoma tumor microenvironment.Results:A total of 51 hub ANRGs closely associated with the tumor microenvironment were identified,from which 3 genes(MERTK,BNIP3,S100A8)were selected to construct the prognostic model.Significant differences in immune cell activation and immune-related signaling pathways were observed between the high-risk and low-risk groups based on tumor microenvironment analysis(all P<0.05).Additionally,characteristic genes within the osteosarcoma microenvironment were identified in regulation of intercellular crosstalk through the GAS6-MERTK signaling pathway.Conclusion:The prognostic model based on ANRGs and tumor microenvironment demonstrate good predictive power and provide more personalized treatment options for patients with osteosarcoma. 展开更多
关键词 ANOIKIS tumor immune microenvironment BIOINFORMATICS PROGNOSIS OSTEOSARCOMA
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Improving autoencoder-based unsupervised damage detection in uncontrolled structural health monitoring under noisy conditions
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作者 Yang Kang Wang Linyuan +4 位作者 Gao Chao Chen Mozhi Tian Zhihui Zhou Dunzhi Liu Yang 《仪器仪表学报》 EI CAS CSCD 北大核心 2024年第6期91-100,共10页
Structural health monitoring is widely utilized in outdoor environments,especially under harsh conditions,which can introduce noise into the monitoring system.Therefore,designing an effective denoising strategy to enh... Structural health monitoring is widely utilized in outdoor environments,especially under harsh conditions,which can introduce noise into the monitoring system.Therefore,designing an effective denoising strategy to enhance the performance of guided wave damage detection in noisy environments is crucial.This paper introduces a local temporal principal component analysis(PCA)reconstruction approach for denoising guided waves prior to implementing unsupervised damage detection,achieved through novel autoencoder-based reconstruction.Experimental results demonstrate that the proposed denoising method significantly enhances damage detection performance when guided waves are contaminated by noise,with SNR values ranging from 10 to-5 dB.Following the implementation of the proposed denoising approach,the AUC score can elevate from 0.65 to 0.96 when dealing with guided waves corrputed by noise at a level of-5 dB.Additionally,the paper provides guidance on selecting the appropriate number of components used in the denoising PCA reconstruction,aiding in the optimization of the damage detection in noisy conditions. 展开更多
关键词 structural health monitoring guided waves principal component analysis deep learning DENOISING dynamic environmental condition
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新课程下中学政治课教学的创新 被引量:1
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作者 车文友 《科技资讯》 2009年第13期186-186,共1页
新课程的改革脚步已进入了中学课堂教学,并不断地深入和发展。教师在教学中要着重开发学生的创造潜能,把发展创造力作为教学核心,培养学生的探索精神,培养自学能力,让课堂充满着跳跃的音符,创造的活力。建立新型师生关系,设置创新环境;... 新课程的改革脚步已进入了中学课堂教学,并不断地深入和发展。教师在教学中要着重开发学生的创造潜能,把发展创造力作为教学核心,培养学生的探索精神,培养自学能力,让课堂充满着跳跃的音符,创造的活力。建立新型师生关系,设置创新环境;激发学生学习兴趣,培养创新意识;营造课堂"敢问"氛围,培养质疑能力;鼓励学生求异发散思维;注重社会课堂实践,完善创新能力。 展开更多
关键词 政治课教 创新教育 创新意识 创新环 创新
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Influence of Soil Geochemistry to the Quality of Winter Jujube in Zhanhua 被引量:1
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作者 高宗军 王敏 +1 位作者 庞绪贵 刘中业 《Agricultural Science & Technology》 CAS 2010年第9期209-212,216,共5页
[Objective] The aim was to investigate the effects of soil geochemistry on the quality of winter jujube.[Method]Based on the data of ecological geochemical survey in lower Yellow River Basin,the relevance of the geoch... [Objective] The aim was to investigate the effects of soil geochemistry on the quality of winter jujube.[Method]Based on the data of ecological geochemical survey in lower Yellow River Basin,the relevance of the geochemistry environment in top soils and the quality of winter jujubes was analyzed.[Result]Cd,Ni and other heavy metals in the soil more obviously affected the nutrition of winter jujubes.[Conclusion]B,Mn,MgO,Cd,Zn,K2O and other elements in the root soil played an important role in the enrichment of Cr and Hg of winter jujube fruit.And the absorption of heavy metals in winter jujube root could be interfered by improving fertilization method,to reduce the enrichment of harmful elements in jujube fruit. 展开更多
关键词 Zhanhua winter jujube Ecological geochemical environment Heavy metal element
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Value evaluation of ecological risk of marine chemical spills 被引量:1
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作者 张继伟 杨志峰 +1 位作者 汤军健 陈楚汉 《Marine Science Bulletin》 CAS 2010年第2期74-84,共11页
The environmental risk of chemical spills near coastal zones threatens abundant marine ecological resources. By appraising the ecological damage value of the environmental risk of marine chemical spills, we can facili... The environmental risk of chemical spills near coastal zones threatens abundant marine ecological resources. By appraising the ecological damage value of the environmental risk of marine chemical spills, we can facilitate decision-making for the development of a coastal zone and establishment of economic policy on coastal zone management. In this study, the ecological effect of the environmental risk of a chemical spill in the Haicang chemical industrial park in Xiamen was identified, after which its impact was forecasted and its ecological damage value was assessed. The information generated in this study will be useful in future studies evaluating marine ecological compensation based on environmental risk analysis. 展开更多
关键词 MARINE chemical spill environmental risk assessment of ecological damage value
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Living characteristics of rare and endangered species Davidia involucrata 被引量:5
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作者 吴钢 韩单恒 +3 位作者 王宏昌 罗跃初 邓红兵 赵景柱 《Journal of Forestry Research》 SCIE CAS CSCD 2004年第1期39-44,J002,共7页
Dovetree (Davidia involucrate), one of the first-class protective plants in China, is a relic species of paleotropical kingdom in Tertiary period, belonging toDavidiaceae with a single genus. In recent years, the incr... Dovetree (Davidia involucrate), one of the first-class protective plants in China, is a relic species of paleotropical kingdom in Tertiary period, belonging toDavidiaceae with a single genus. In recent years, the increase of regional developing projects has led to a sharp decrease of this ancient and rare plant in naturally distributed habitats and natural population. In this paper, the biological and ecological characteristics of Dovetree were described, and the geographically distributed condition of this species in different geologic periods as well as the major reasons for dynamic changes of its population were systematically analyzed in accordance with field researches and references. The investigations conducted in different years by setting up standard sample plots showed that the population number of Dovetree increased yearly in the areas without human interference but decreased yearly in the areas with human interference. With the increase of population density and human activities decreased as the logarithmic curve:Y=?100.7ln(x)+178.09, and it has turned from a dominant population into an endangered population. Based on the former and present studies on Dovetree, some protection strategies were put foreword for protecting this ancient and rare species. Keywords Davidia involucrate - Dovetree - Geographical Distribution - Biological Characteristics - Protection Policy CLC number S718.4 Document code A Article ID 1007-662X(2004)01-0039-06 Foundation Item: This research was coordinated by the National Natural Science Foundation of China (No. 39970591)Biography: Wu Gang (1965-), Male, Professor in Key Laboratory of Systems Ecology, Research Center for Eco Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.Responsible editor: Chai Ruihai 展开更多
关键词 Davidia involucrate Dovetree Geographical Distribution Biological Characteristics Protection Policy
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Rock-forming mechanism of Qingshanjiao intrusion in Dongguashan copper(gold) deposit, Tongling area, Anhui province, China
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作者 刘忠法 邵拥军 +1 位作者 隗含涛 汪程 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2016年第9期2449-2461,共13页
Dongguashan deposit is a large porphyry-skarn copper(gold) deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magm... Dongguashan deposit is a large porphyry-skarn copper(gold) deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional. 展开更多
关键词 Qingshanjiao intrusion geological and geochemical characteristics rock-forming and geodynamic setting magma derivation rock-forming Dongguashan copper(gold) deposit
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Research and countermeasures on how to improve English parole competence of contemporary college students under non-target language environment
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作者 任重远 《Sino-US English Teaching》 2009年第4期15-22,共8页
Based on linguistic theories which developed by Saussure and some other contemporary linguists, this article attempts to analyze the factors that cause low English parole competence of the contemporary college student... Based on linguistic theories which developed by Saussure and some other contemporary linguists, this article attempts to analyze the factors that cause low English parole competence of the contemporary college students under non-target language environment. It views that how to properly deal with the relationship between langue and parole is still a debating focus in applied linguistics. The result of low English parole competence of contemporary college students is due to the interaction of the contemporary College English syllabus, text books pedagogies and the English language level of both students and teachers. Thus it puts forward some suggestions to improve the college students' English parole competence. 展开更多
关键词 non-target language environment college English teaching COUNTERMEASURE RESEARCH
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On the vocabulary acquisition theories and vocabulary teaching of foreign languages
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作者 李庆新 《Sino-US English Teaching》 2009年第1期1-4,共4页
As one of the important phases of language acquisition process, vocabulary acquisition has great impact on one's language competence and communication competence. However, there are still some problems in students' ... As one of the important phases of language acquisition process, vocabulary acquisition has great impact on one's language competence and communication competence. However, there are still some problems in students' vocabulary acquisition. This paper first discusses the current problems in vocabulary teaching, and then analyzes some laws in vocabulary acquisition, and at last it discusses the advantages of making use of Internet in vocabulary teaching, which aims to find a possible solution to the problems. 展开更多
关键词 tabular acquisition vocabulary teaching Internet environment language competence
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Isothermal Microcalorimetry:A Review of Applications in Soil and Environmental Sciences 被引量:9
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作者 RONG Xing-Min HUANG Qiao-Yun JIANG Dai-Hua CAI Peng LIANG Wei 《Pedosphere》 SCIE CAS CSCD 2007年第2期137-145,共9页
Isothermal microcalorimetry provides thermodynamic and kinetic information on various reactions and processes and is thereby a powerful tool to elucidate their mechanisms. Certain improvement in isothermal microcalori... Isothermal microcalorimetry provides thermodynamic and kinetic information on various reactions and processes and is thereby a powerful tool to elucidate their mechanisms. Certain improvement in isothermal microcalorimetry with regard to the studies on soil and environmental sciences is briefly described. This review mainly focuses on the use of microcalorimetry in the determination of soil microbial activity, monitoring the toxicity and biodegradation of soil organic pollutants, the risk evaluation of metals and metalloids, the heat effect of ion exchange and adsorption in soil, and environmental researches. Promising prospects for the applications of the technique in the field are also discussed. 展开更多
关键词 ENVIRONMENT ISOTHERMAL microbial activity MICROCALORIMETRY SOIL
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RESIDENTS' ATTITUDES TO TOURISM DEVELOPMENT IN ANCIENT VILLAGE RESORTS——Case Study of World Cultural Heritage of Xidi and Hong Villages 被引量:8
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作者 WANGLi TONGShi-rong +3 位作者 LUSong YANGZhao WANGYong LIANGDong-dong 《Chinese Geographical Science》 SCIE CSCD 2004年第2期170-178,共9页
Tourism development surely has social, economic and environmental impacts on tourist destinations.The study on resorts residents' attitudes can help understand the nature of tourism development and the extent to w... Tourism development surely has social, economic and environmental impacts on tourist destinations.The study on resorts residents' attitudes can help understand the nature of tourism development and the extent to which it may influence on tourist destinations. By now, researches on residents' perception and attitudes are plenteous in the international circle and achievements are great, yet few are found in developing countries. As a most representative cultural tourist destination, World Cultural Heritage-Xidi and Hong villages in Yi County of Anhui Province, are drawing the attention of both tourists and academic circles. This article, taking Xidi and Hong villages as examples, seeks to analyze ancient village residents' attitudes towards tourism impacts and then tries further to explore the connection between tourism development and residents' attitudes. Both qualitative and quantitative surveys are applied in the exploratory investigation into local residents' attitudes of tourism impacts. Based on abundant face-to-face interviews with the local households, tourism enterprises concerned, local government and tourists from July to August of 2002, we are able to have a better understanding of local residents' attitudes to community life, and perception of tourism impacts on society, economy and environment. By this we can promote domestic study on resorts residents' attitudes, and provide some theoretical grounds for establishing tourism development planning and perfect community participation system at tourist destinations. 展开更多
关键词 ancient village resort Xidi and Hong villages residents' attitudes
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EVOLVEMENT AND CONTROL OF VULNERABLE ECOLOGICAL REGION—A Case Study in Ongniud Banner and Aohan Banner,Inner Mongolia 被引量:3
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作者 RANSheng-hong JINJian-jun 《Chinese Geographical Science》 SCIE CSCD 2004年第2期135-141,共7页
The evolvement of a vulnerable ecological region is a dynamic process, which is affected by various factors. During the evolvement process, human activities have a decisive effect. The purpose of studying vulnerable e... The evolvement of a vulnerable ecological region is a dynamic process, which is affected by various factors. During the evolvement process, human activities have a decisive effect. The purpose of studying vulnerable ecological region is to control human economic activities and to develop a negative feedback modulation mechanism.This paper established a model of vulnerable ecological region's evolvement by considering four synthetic variables.These synthetic variables are ecological carrying capacity, ecological resilience, economic development intensity, and economic development velocity. Finally, Ongniud Banner and Aohan Banner in North China were taken as study cases to simulate the evolvement processes of vulnerable ecological regions under different conditions of economic development. The results show that human activities have an important influence on the evolvement trend of vulnerable ecological region. 展开更多
关键词 vulnerable ecological region ecological evolvement ecological control SIMULATION Ongniud Banner Aohan Banner
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Integrated controlling technique of ecological environment in Shendong Mining Area 被引量:6
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作者 张东升 刘玉德 +1 位作者 王安 王义 《Journal of Coal Science & Engineering(China)》 2007年第4期471-475,共5页
To enclose the interactive relation between the underground mining with suitable protection for surface ecological environments and surface prevention of ecological environments adapting to mining disturbing was resea... To enclose the interactive relation between the underground mining with suitable protection for surface ecological environments and surface prevention of ecological environments adapting to mining disturbing was researched and developed core of this technique. There are three aspects of controlling ecological environments, to dispose and renew before exploitation, to protect surface ecological environments in the exploitative process and to repair and build up after exploitation. Based on the moving law of overburden strata in shallow seam, the surface subsidence law and the growth law of vegetation in subsidence mine area, the integrated controlling technique has been developed synthetically by methods of theoretic analysis, laboratory simulation, numerical calculation, commercial test etc.. It includes the key techniques of aquifer-protective mining, filtering and purging of mine water through goaf, preventing and extinguishing fire in shallow seam no-rock roadway layout and waste disposal in underground, frame-building ecological functional sphere before exploitation, frame-building the ecological cycle using system after mining and so on. 展开更多
关键词 controlling ecological environments desert area large-scale exploitation aquifer-protective mining ecological functional sphere
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Olympic torch relay abroad and its reflection on English teaching at home
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作者 陈玉玲 殷超 《Sino-US English Teaching》 2009年第12期9-12,46,共5页
What happened to the Olympic torch relay abroad reveals how little and superficially the western countries, in particular, know of china. Meanwhile there also exists a lack or vacancy of English teaching in English te... What happened to the Olympic torch relay abroad reveals how little and superficially the western countries, in particular, know of china. Meanwhile there also exists a lack or vacancy of English teaching in English teaching at home. The failure of expressing Chinese culture and conditions correctly and fluently among the English learners has already resulted in negative impact on our international image, which is related to our teaching policy of strengthening western culture and neglecting the export of our own culture. Therefore, in the English teaching at all levels, great attention should be paid to the cross-cultural communication between home culture and the culture of target language, the promotion of expressing mother culture in foreign languages, and exporting and broadcasting Chinese culture. 展开更多
关键词 the Olympic torch relay abroad English teaching
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Ecology of macrozoobenthic communities in two plateau lakes of Southwest China 被引量:5
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作者 崔永德 王洪铸 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2008年第4期345-352,共8页
Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytop... Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl α=99.76±24.01 μg/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being I 423 ind/m^2 and 8.71 g/m^2 in XL and 4 249 ind/m^2 and 8.60 g/m^2 in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffrneisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes. 展开更多
关键词 plateau lakes macrozoobenthos taxonomic composition standing crop functional feeding group environmental analysis
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Expression and characterization of a bifunctional alginate lyase named Al163 from the Antarctic bacterium Pseudoalteromonas sp. NJ-21 被引量:3
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作者 XIE Maisheng LI Jiang +1 位作者 HE Peiqing LIN Xuezheng 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2018年第4期1304-1314,共11页
In this study, an endolytic alginate lyase, named Al163, was identified, cloned, and characterized from the Antarctic bacterium Pseudoalteromonas sp. NJ-21. Comparative sequence analysis showed that the predicted amin... In this study, an endolytic alginate lyase, named Al163, was identified, cloned, and characterized from the Antarctic bacterium Pseudoalteromonas sp. NJ-21. Comparative sequence analysis showed that the predicted amino acid sequence encoded by al163 belongs to the polysaccharide lyase 6(PL-6) family and has a molecular mass of about 80 kDa. Recombinant enzyme was purified by Ni-Sepharose affinity chromatography. Recombinant Al163 exhibited maximum activity(258 U/mg) at pH 7.0 and 40℃, and thermal stability assays showed retention of almost 90% activity after incubation at 30℃ for 30 min. Al163 activity was stimulated by Cd^(2+), Ca^(2+), Fe^(3+), and Mn^(2+), but inhibited by Cu^(2+), Si^(2+), Fe^(2+), and Ni^(2+). Thin-layer chromatographic analysis indicated that Al163 degraded sodium alginate, poly M, and poly G, generating disaccharides and trisaccharides as the final products. Only a few bacterial strains that produce a bifunctional alginate lyase have been reported. Our results indicate that recombinant Al163 exhibits broad substrate specificity and its products exhibit low degrees of polymerization. Both properties imply high potential for use of the enzyme in several industrial fields, including cosmetics and pharmaceuticals, based on the high demand for biologically active oligosaccharides. 展开更多
关键词 Pseudoalteromonas sp. alginate lyase PL-6 family
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