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Review: update on performance assessment and monitoring systems for ophthalmologists
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作者 Heather G.Mack 《Annals of Eye Science》 2024年第1期24-33,共10页
Performance assessment and monitoring systems are the process by which ophthalmologists demonstrate they are fit to continue practicing.Revalidation is the process by which licensed doctors are legally required to dem... Performance assessment and monitoring systems are the process by which ophthalmologists demonstrate they are fit to continue practicing.Revalidation is the process by which licensed doctors are legally required to demonstrate to medical regulators that they are up to date and fit to practice in order to maintain their medical license,and began in the United Kingdom(UK)in 2012 following well-publicized events.Recertification is a different process which began in North America and demonstrates doctors have maintained competence,without involvement of external stakeholders.Arguments for and against the concept of performance assessment are reviewed.Stakeholders in performance assessment,whether part of the process or not,are doctors themselves,peers and other health care providers,patients,hospitals and health systems,medical regulators,and health policy makers.Early models of performance assessment included portfolios,credit accumulation,and closed-book examinations.Models are in evolution with the value of formative rather than summative assessments,and the need for methods of assessing procedural competency increasingly recognized.Emerging methods of performance assessment of practicing ophthalmologists include use of performance indicators,simulation,and workplace-based assessments.Alternate methods of assuring the public by improved detection of outliers are discussed.Despite weak evidence supporting performance assessments in demonstrating continuing competency to practice,the process is gradually being accepted worldwide.Further research into optimum methods of performance assessment and monitoring processes is required,along with cost-benefit analysis. 展开更多
关键词 performance assessment REVALIDATION RECERTIFICATION maintenance of competency relicensure
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Environmental performance assessments of different methods of coal preparation for use in small-capacity boilers: experiment and theory
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作者 A.N.Kozlov E.P.Maysyuk I.Yu.Ivanova 《International Journal of Coal Science & Technology》 EI CAS CSCD 2023年第5期57-71,共15页
The purpose of this article is to receive environmental assessments of combustion of different types of coal fuel depending on the preparation(unscreened,size-graded,briquetted and heat-treated)in automated boilers an... The purpose of this article is to receive environmental assessments of combustion of different types of coal fuel depending on the preparation(unscreened,size-graded,briquetted and heat-treated)in automated boilers and boilers with manual load-ing.The assessments were made on the basis of data obtained from experimental methods of coal preparation and calculated methods of determining the amount of pollutant and greenhouse gas emissions,as well as the mass of ash and slag waste.The main pollutants from coal combustion are calculated:particulate matter,benz(a)pyrene,nitrogen oxides,sulfur dioxide,carbon monoxide.Of the greenhouse gases carbon dioxide is calculated.As a result of conducted research it is shown that the simplest preliminary preparation(size-graded)of coal significantly improves combustion efficiency and environmental performance:emissions are reduced by 13%for hard coal and up to 20%for brown coal.The introduction of automated boil-ers with heat-treated coal in small boiler facilities allows to reduce emissions and ash and slag waste by 2-3 times.The best environmental indicators correspond to heat-treated lignite,which is characterized by the absence of sulfur dioxide emissions. 展开更多
关键词 Coal preparation Automated and hand-fed coal boilers environmental performance metrics
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Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei 被引量:2
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作者 Shicheng Su Nianqing Jin Xiaoli Wei 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第1期12-28,共17页
Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in... Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory.In this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei seedlings.The canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following thin-ning.Thinning improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light environ-ment.Under the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral composition.P.bournei photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light environment.In a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal conductance.As a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of P.bournei seedlings,and a reduction increased light absorption and use capacity and height:diameter ratios.The growth advantage transformed from diameter to height,enabling seedlings to access more light.Our findings suggest that the regeneration of shade-tolerant species such as P.bournei could be enhanced if a targeted approach to thinning based on stand type was adopted. 展开更多
关键词 THINNING Understory light environment Phoebe bournei Photosynthetic performance Growth performance
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The Influence of Information Technology Investment on the Organizational Performance:The Moderating Role of External Environment
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作者 Zhilin Shi Simon Choong Mun Kwong 《Proceedings of Business and Economic Studies》 2024年第5期37-42,共6页
In the information era,enterprises can enhance organizational performance through advanced information technology.Based on the resource-based view,this paper examines the mechanism by which information technology(IT)i... In the information era,enterprises can enhance organizational performance through advanced information technology.Based on the resource-based view,this paper examines the mechanism by which information technology(IT)investment influences organizational performance,with the external environment as a moderating variable.Using 265 valid samples collected from agricultural enterprises in Shandong province,this study conducts an empirical test through partial least squares structural equation modeling.The results demonstrate that IT investment has a significant positive effect on organizational performance,and the external environment significantly moderates the relationship between IT investment and organizational performance.This research contributes to a deeper understanding of the relationship between IT investment and organizational performance,enriches resource-based theory,expands the research framework on IT investment,and offers guidance for enterprises seeking sustainable growth. 展开更多
关键词 IT investment Organizational performance External environment
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Design strategy and comprehensive performance assessment towards Zn anode for alkaline rechargeable batteries
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作者 Di Yang Jinsheng Li +2 位作者 Changpeng Liu Wei Xing Jianbing Zhu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2023年第7期122-138,I0004,共18页
Alkaline Zn-based primary batteries have been commercialized in the past decades.However,their success has not been extended to secondary batteries due to the poor cycle reversibility of Zn anodes.Although some resear... Alkaline Zn-based primary batteries have been commercialized in the past decades.However,their success has not been extended to secondary batteries due to the poor cycle reversibility of Zn anodes.Although some research has been conducted on alkaline Zn anodes,their performance is still far from commercial requirements.A variety of degradation mechanisms,including passivation,dendrites,morphological changes,and hydrogen precipitation,are claimed responsible for the failure of alkaline Zn metal anodes.What’s worse,these constraints always interact with each other,which leads to a single strategy being unable to suppress all the issues.Therefore,a comprehensive evaluation of the positive and negative effects of various strategies on performance is important to promote the commercialization of alkaline Zn batteries.Herein,the recent progress and performance of improvement strategies for Zn anode in alkaline conditions are reviewed systematically.First,the principles and challenges of alkaline Zn anodes are briefly analyzed.Then,various design strategies for alkaline Zn anodes from the perspectives of ion and electron regulation are highlighted.Last,through a comprehensive summary of various performance parameters,the advantages and disadvantages of different strategies are compared and evaluated.On the basis of this assessment,we aim to provide more insights into the anode design of high-performance alkaline rechargeable Zn batteries. 展开更多
关键词 Alkaline aqueous batteries Zinc anode Regulation strategies performance assessment
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A climatic environmental performance assessment method for ecological city construction:Application to Beijing Yanqi Lake 被引量:1
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作者 FANG Xiao-Yi CHENG Chen +3 位作者 LIU Yong-Hong DU Wu-Peng XIAO Xiao-Jun DANG Bing 《Advances in Climate Change Research》 SCIE CSCD 2015年第1期23-35,共13页
In contrast to the input perspective for evaluating planning metrics, this research takes the climatic environmental output effects as the starting point for assessing ecological city construction. Based on approaches... In contrast to the input perspective for evaluating planning metrics, this research takes the climatic environmental output effects as the starting point for assessing ecological city construction. Based on approaches such as observation data analysis, meteorological model simulation, and remote sensing, a set of climatic environmental performance assessment methods is developed and established. These methods mainly focus on surface ventilation assessment and urban thermal environment assessment. With the Yanqi Lake ecological development demonstration area located in Huairou district, Beijing as an example, the assessment of the local climatic environment before and after the construction are conducted, and relevant policy suggestions for urban planning and construction are presented. The results show that after development, the ventilation capacity will decrease overall and the ventilation potential index will decrease from 0.53 to 0.44. While this is not a large reduction, and is still at a favorable level, the ventilation potential in some local areas will markedly decrease. Furthermore, the thermal environment will become poorer to some extent; the urban heat island(UHI) area and intensity will increase compared with the current situation;continuous heat islands may occur in local areas; the UHI potential index of the core area will rise from 0.0878 to 0.1217(still a favorable level).Therefore, urban surfaces should be carefully developed and arranged during planning. It is suggested that the negative impacts of large areas of urban construction on the local climatic environment in the Yanqi Lake could be mitigated by 1) strengthening the airflow by introducing fresh,cold, northwesterly air via constructed ventilation corridors, 2) increasing the number of ecological cold sources, particularly for water bodies and green belts to prevent the UHI in the southern region of Yanqi Lake from becoming linked with each other, and 3) considering a pre-program before sub-domain and building planning to obtain optimum building locations. Different construction standards should be developed for different ventilation potential and UHI intensity levels. For strong heat island areas, land areas should be reserved to serve as cold sources. 展开更多
关键词 Ecological city construction Ventilation environment Thermal environment performance assessment Yanqi Lake ecological development demonstration area
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Environmental Impact Assessment of Onshore Wind Farms in the Region of Central Greece Using a Modified RIAM Method
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作者 Olga Korozi Dimitra G.Vagiona 《Journal of Environmental & Earth Sciences》 CAS 2024年第1期71-82,共12页
Wind energy is one of the most basic forms of renewable energy,which shows an increasing rate of development worldwide and also at the European level.However,this rapid deployment of wind farms makes the need for an i... Wind energy is one of the most basic forms of renewable energy,which shows an increasing rate of development worldwide and also at the European level.However,this rapid deployment of wind farms makes the need for an impact assessment of this type of projects on the natural and man-made environment imperative.The present paper aims to identify and assess the environmental impacts of wind farm projects in the Region of Central Greece.A modified Rapid Impact Assessment Matrix(RIAM)method is used for this purpose.The methodology includes the identification of the existing onshore wind farm projects in the study area,the appropriate modifications of the RIAM method to respond to the characteristics of the projects and the study area,the qualitative assessment of their potential impacts during construction and operational phases and the computation of the Environmental Performance Grade(EPG)of projects based on the pro-posed modified RIAM method.The results reveal that although there are some slight negative impacts on the natural environment of the study area,the examined wind farms contribute positively both to the atmosphere and to the socio-economic environment of the study.This study extends the potential for using RIAM as a tool in environmental impact assessment studies of renewable energy projects. 展开更多
关键词 environmental impact assessment environmental components Region of central Greece Rapid impact assessment matrix(RIAM) environmental performance grade(EPG)
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Target acquisition performance in the presence of JPEG image compression
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作者 Boban Bondzulic Nenad Stojanovic +3 位作者 Vladimir Lukin Sergey A.Stankevich Dimitrije Bujakovic Sergii Kryvenko 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第3期30-41,共12页
This paper presents an investigation on the effect of JPEG compression on the similarity between the target image and the background,where the similarity is further used to determine the degree of clutter in the image... This paper presents an investigation on the effect of JPEG compression on the similarity between the target image and the background,where the similarity is further used to determine the degree of clutter in the image.Four new clutter metrics based on image quality assessment are introduced,among which the Haar wavelet-based perceptual similarity index,known as HaarPSI,provides the best target acquisition prediction results.It is shown that the similarity between the target and the background at the boundary between visually lossless and visually lossy compression does not change significantly compared to the case when an uncompressed image is used.In future work,through subjective tests,it is necessary to check whether this presence of compression at the threshold of just noticeable differences will affect the human target acquisition performance.Similarity values are compared with the results of subjective tests of the well-known target Search_2 database,where the degree of agreement between objective and subjective scores,measured through linear correlation,reached a value of 90%. 展开更多
关键词 JPEG compression Target acquisition performance Image quality assessment Just noticeable difference Probability of target detection Target mean searching time
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Environmental Assessment and Dielectric Performances of the Secondary Electrical Insulation in Low Voltage Motors Impregnated by Different Techniques
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作者 Manh Quan Nguyen Simon Dario +4 位作者 David Malec Dominique Mary Jean-Pascal Cambronne Damien Prunel Julie Orgelet 《Engineering(科研)》 2017年第10期860-873,共14页
A recent technique, using to potentially replace the conventional impregnating one in low voltage electric motors, has been studied in this communication. The conventional technique that uses?both primary and secondar... A recent technique, using to potentially replace the conventional impregnating one in low voltage electric motors, has been studied in this communication. The conventional technique that uses?both primary and secondary insulations;?i.e.: enamel and varnish, has been compared to this recent technique which only uses one component,?i.e.: self-bonding wires. Self-bonding wires polymerization is very quick compared to that of the conventional technique. Environmental impact and both dielectric and mechanical properties of these two techniques have been estimated and compared. The goal is to estimate if this recent technique has not only a better environmental footprint but also good technical properties. The dielectric properties that have been measured are the dielectric strength and?the lifetime under pulse?voltage while mechanical consists in measuring the bonding strength that is crucial for impregnation.?For that purpose, a Life Cycle Assessment (LCA) that can simultaneously evaluatenumerous impacts on ground, water and air,?has been performed. The results show clearly that the recent technique significantly reduces the environmental footprint. Both mechanical and dielectric properties are then compared and analyzed. 展开更多
关键词 Electrical MOTOR Enameled WIRE Self-Bonding WIRE IMPREGNATION Tech-nique Dielectric performance environmental Impact
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From EBIT to SEBIT(Sustainable EBIT):Sustainable Performance Accounting(SPA)Using the Example of CO_(2) Accounting
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作者 Knut Henkel Jenny Lay-Kumar Christian Hiß 《Journal of Modern Accounting and Auditing》 2024年第2期49-71,共23页
Corporate sustainability reporting has become increasingly important in recent years.However,conventional approaches reach their limits when it comes to quantifying and measuring the actual sustainability performance ... Corporate sustainability reporting has become increasingly important in recent years.However,conventional approaches reach their limits when it comes to quantifying and measuring the actual sustainability performance of a company.This article presents a new approach:Sustainable Performance Accounting(SPA),which is based on an extension of bookkeeping by including ESG bookkeeping.SPA enables companies to systematically measure and manage their sustainability performance.The article provides an overview of the basics of SPA methodology and uses a comprehensive example showing how SPA can be implemented in practice.The article is aimed at interested readers from science and practice as well as decision-makers who are interested in future-oriented sustainability reporting. 展开更多
关键词 CO_(2)accounting CO_(2)emissions CSRD ESG(environmental Social Governance) ESG bookkeeping ESG provision ESG asset ESRS integrated financial reporting internalisation of external effects connectivity monetisation of ESG issues sustainability sustainability indicators negative emissions sequestration performance Sustainable performance Accounting(SPA)
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Enhancing Learners’Performance in Grade 7 Mathematics Through 50-30-20 Exercise
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作者 Joniel S.Cerbito 《Journal of Contemporary Educational Research》 2024年第1期233-245,共13页
Assessment exercises constitute a crucial component of the teaching and learning process,serving the purpose of gauging the degree to which learning objectives have been accomplished.This study aims to assess the math... Assessment exercises constitute a crucial component of the teaching and learning process,serving the purpose of gauging the degree to which learning objectives have been accomplished.This study aims to assess the mathematics performance of Grade 7 learners using the 50-30-20 exercise.Specifically,this study seeks to determine the learners’pre-test and post-test mean scores,identify significant differences between the pre-test and post-test results,evaluate learners’exercises,and propose enhanced exercises.The research employs a quasi-experimental design,with 40 Grade 7 learners in the school year 2023-2024 as participants,selected through purposive non-random sampling.Statistical data analysis involves the use of mean,standard deviation,paired t-test,and Cohen’s D effect size.Ethical considerations were paramount,as evidenced by a letter of authorization from the school head outlining the strict adherence to voluntary participation,informed parental consent,anonymity,confidentiality,risk mitigation,results-sharing protocols,and the commitment to keeping research data confidential.The data yielded a remarkable outcome:the experimental group exhibited improvement in both the pre-test and post-test.This result substantiates the initial objective of the study,showcasing a noteworthy and favorable performance among the participants.Consequently,it suggests that a majority of the participants strongly agree that the 50-30-20 exercises contribute to enhancing their understanding and problem-solving skills,as well as their ability to grasp mathematical concepts and improve their overall performance in mathematics.Therefore,the 50-30-20 exercises not only facilitated students in understanding mathematics lessons but were also aligned with the Department of Education’s development plan. 展开更多
关键词 Mathematical assessment exercises Learners’mathematical performance 50-30-20 exercises
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A Simulation Model for Road and Maritime Environmental Performance Assessment
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作者 J.J.Usabiaga M.Castells +1 位作者 F.X.Martínez, A.Olcer 《Journal of Environmental Protection》 2013年第7期683-693,共11页
The White Paper published in 2011, Roadmap to a Single European Transport Area [1], urges on a 30% modal shift of road freight over 300 km to other modes (rail, maritime and inland waterways) by 2030, and more than 50... The White Paper published in 2011, Roadmap to a Single European Transport Area [1], urges on a 30% modal shift of road freight over 300 km to other modes (rail, maritime and inland waterways) by 2030, and more than 50% by 2050. However the environmentally friendly performance of maritime transport regarding air pollutant emissions in comparison with road transport is in doubt. This paper presents a three dimension simulation model, in which performed transport work, arisen emissions and produced impact are estimated and inter-related for the assessment of the environmental performance of both road and maritime transport. The simulation model will be a valuable decision making tool for policymakers as it enables the precise assessment of considered transport alternatives in the EU27 until 2020, and hence supports the design of future intervening actions. 展开更多
关键词 TRANSPORT EMISSIONS environmental performance Policy assessment
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Impact of Network and Environment Conditions on the Performance Assessment of Energy Efficient Dynamic Routing Protocol for Wireless Ad Hoc Networks
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作者 Dina Darwish 《通讯和计算机(中英文版)》 2012年第2期189-199,共11页
关键词 动态路由协议 网络类型 性能评估 高效节能 无线AD 环境 无线通讯 无线网络
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Application of Formative Assessment to Improve Art Students’Oral Eng lish Performance
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作者 邓慧萍 《海外英语》 2021年第11期291-292,共2页
This paper focuses on the advantages of formative assessment and explores a better application of it in English class to facilitate art students’learning and further improve their oral English performance.
关键词 Formative assessment oral English performance art students
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Assessment of bearing performance degradation via extension and EEMD combined approach 被引量:18
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作者 LIU Yu-mei ZHAO Cong-cong +3 位作者 XIONG Ming-ye ZHAO Ying-hui QIAO Ning-guo TIAN Guang-dong 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第5期1155-1163,共9页
As a key component in rotating machinery, the operating reliability of bearing influences the performance and service life of the equipment directly. In order to describe bearing performance degradation(BPD) process e... As a key component in rotating machinery, the operating reliability of bearing influences the performance and service life of the equipment directly. In order to describe bearing performance degradation(BPD) process effectively, an assessment approach combining extension and ensemble empirical mode decomposition(EEMD) was proposed. First, the extension was utilized to construct the matter-element of bearing operating state, and the energy moment of intrinsic mode functions(IMFs) was used as characteristic parameter of the matter-element. Then, to determine classical domains of characteristic parameters, the mathematical statistics method was adopted. Finally, the BPD was analyzed qualitatively and quantitatively according to the comprehensive correlation degree of bearing current operating state related to its healthy state. The analytic results of bearing test-rig show that the proposed method indicates the incipient fault approximately occurring in the 81 st hour, and the method also quantitatively presents the degree of BPD. By contrast, the BPD assessment based on time-domain features extraction method could not achieve the above two results effectively. 展开更多
关键词 BEARING performance degradation assessment EXTENSION ENSEMBLE empirical mode decomposition MATHEMATICAL STATISTICS
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Leveraging core capabilities and environmental dynamism for food traceability and firm performance in a food supply chain: A moderated mediation model 被引量:13
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作者 SONG Mo-xi YANG Morgan Xin 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2019年第8期1820-1837,共18页
This paper develops a moderated mediation model in which the interactive effects of food traceability and environmental dynamism on firm performance are mediated by the core capabilities(operating capabilities and mar... This paper develops a moderated mediation model in which the interactive effects of food traceability and environmental dynamism on firm performance are mediated by the core capabilities(operating capabilities and marketing capabilities)in food supply chain context, by invoking the indirect view of organizational learning theory. Our hypotheses were tested using hierarchical regression and bootstrapping methods with a sample of 216 food manufacturing firms in China, and a survey-based, two-informant design was used to collect data. The results revealed that operating and marketing capabilities fully mediate the food traceability-performance link. In addition, environmental dynamism positively moderates the food traceability-core capabilities link. Moreover, it is found that operating and marketing capabilities transform the interactive impacts of environmental dynamism and food traceability into firm performance. Our study offers a fine-grained picture of the essential food traceability-performance link by revealing for the first time that there is an interactive impacts of food traceability and environmental dynamism on firm performance via core capabilities. 展开更多
关键词 FOOD TRACEABILITY operating capabilities marketing capabilities ORGANIZATIONAL learning environmental DYNAMISM FOOD FIRM performance China
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High resolution radar target adaptive detector and performance assessment 被引量:7
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作者 Tao Jian You He Feng Su Changwen Qu Dianfa Ping 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2011年第2期212-218,共7页
The high resolution radar target detection is addressed in the non-Gaussian clutter. An adaptive detector is derived for range-spread target based on a novel covariance matrix estimator. It is proved that the new dete... The high resolution radar target detection is addressed in the non-Gaussian clutter. An adaptive detector is derived for range-spread target based on a novel covariance matrix estimator. It is proved that the new detector is constant false alarm rate (CFAR) to both of the clutter covariance matrix structure and power level theoretically for match cases. The simulation results show that the new detector is almost CFAR for mismatch cases, and it outperforms the existing adaptive detector based on the sample covariance matrix. It also shows that the detection performance improves, as the number of pulses, the number of secondary data or the clutter spike increases. In addition, the derived detector is robust to different subsets, estimated clutter group sizes and correlations of clutter. Importantly, the number of iterations for practical application is just one. 展开更多
关键词 non-Gaussian clutter adaptive detection range-spread target performance assessment.
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Multivariable Control Performance Assessment Based on Generalized Minimum Variance Benchmark 被引量:12
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作者 赵宇 苏宏业 +1 位作者 褚健 古勇 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2010年第1期86-94,共9页
This paper is concerned with the control performance assessment based on the multivariable generalized minimum variance benchmark.An explicit expression for the feedback controller-invariant(the generalized minimum va... This paper is concerned with the control performance assessment based on the multivariable generalized minimum variance benchmark.An explicit expression for the feedback controller-invariant(the generalized minimum variance)term of the multivariable control system is obtained,which is used as a standard benchmark for the assessment of the control performance for multi input multi output(MIMO)process.The proposed approach is based on the multivariable minimum variance benchmark.In comparison with the minimum variance benchmark, the developed method is more reasonable and practical for the control performance assessment of multivariable systems.The approach is illustrated by a simulation example and an industrial application. 展开更多
关键词 control performance assessment generalized minimum variance minimum variance control multi- variable control system
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Application of a Novel Method for Machine Performance Degradation Assessment Based on Gaussian Mixture Model and Logistic Regression 被引量:3
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作者 LIU Wenbin ZHONG Xin +2 位作者 LEE Jay LIAO Linxia ZHOU Min 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第5期879-884,共6页
The currently prevalent machine performance degradation assessment techniques involve estimating a machine's current condition based upon the recognition of indications of failure features,which entail complete data ... The currently prevalent machine performance degradation assessment techniques involve estimating a machine's current condition based upon the recognition of indications of failure features,which entail complete data collected in different conditions.However,failure data are always hard to acquire,thus making those techniques hard to be applied.In this paper,a novel method which does not need failure history data is introduced.Wavelet packet decomposition(WPD) is used to extract features from raw signals,principal component analysis(PCA) is utilized to reduce feature dimensions,and Gaussian mixture model(GMM) is then applied to approximate the feature space distributions.Single-channel confidence value(SCV) is calculated by the overlap between GMM of the monitoring condition and that of the normal condition,which can indicate the performance of single-channel.Furthermore,multi-channel confidence value(MCV),which can be deemed as the overall performance index of multi-channel,is calculated via logistic regression(LR) and that the task of decision-level sensor fusion is also completed.Both SCV and MCV can serve as the basis on which proactive maintenance measures can be taken,thus preventing machine breakdown.The method has been adopted to assess the performance of the turbine of a centrifugal compressor in a factory of Petro-China,and the result shows that it can effectively complete this task.The proposed method has engineering significance for machine performance degradation assessment. 展开更多
关键词 performance degradation assessment Gaussian mixture model logistic regression proactive maintenance sensor fusion
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Performance assessment of water mist applied in gas burning suppression in underground coal mine 被引量:6
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作者 余明高 郑立刚 +3 位作者 刘志超 潘荣锟 贾海林 袁俊 《Journal of Coal Science & Engineering(China)》 2006年第2期48-52,共5页
The main objective of the present study was introduced water mist suppressiontechnology to prevent and control gas burning which occurred during drilling at Wu20160working-face in No.10 coal mine of Pingdingshan Ltd..... The main objective of the present study was introduced water mist suppressiontechnology to prevent and control gas burning which occurred during drilling at Wu20160working-face in No.10 coal mine of Pingdingshan Ltd..Based on the self-developed ex-periment platform,a series of fire suppression tests to evaluate the performance of a watermist system were conducted.The detailed measurements of the spray characteristics,i.e.,the Sauter Mean Diameter(SMD),the velocity and spray angle which are the main pa-rameters considered in the Study,were obtained by using LS-2000 Sizer.The amount ofwater consumed and the water flux density distribution over the cross section downstreamthe nozzle exit were measured by cup collector method.The operating pressure of thewater mist nozzle is set to 0.5 MPa,the droplet SMD of 104 pm,the water flux density dis-tribution from 0.71 to 8.47 L/(m^2.min),the average velocity of 2.14 m/s.The experimentalresults show that the averaged time required for extinguishment is 3.14 s,and the corre-sponding amount of water used during fire test is about 0.11 kg.The gas fire suppressionsystem reduces the temperature in combustion chamber of the experimental apparatusbelow the ignition point of the gas,which can effectively avoid the occurrence of the gasfire in coal mine. 展开更多
关键词 gas burning water mist coal mine fire suppression performance assessment
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