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Detecting Fake News Over Online Social Media via Domain Reputations and Content Understanding
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作者 Kuai Xu Feng Wang +1 位作者 Haiyan Wang Bo Yang 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2020年第1期20-27,共8页
Fake news has recently leveraged the power and scale of online social media to effectively spread misinformation which not only erodes the trust of people on traditional presses and journalisms, but also manipulates t... Fake news has recently leveraged the power and scale of online social media to effectively spread misinformation which not only erodes the trust of people on traditional presses and journalisms, but also manipulates the opinions and sentiments of the public. Detecting fake news is a daunting challenge due to subtle difference between real and fake news. As a first step of fighting with fake news, this paper characterizes hundreds of popular fake and real news measured by shares, reactions, and comments on Facebook from two perspectives:domain reputations and content understanding. Our domain reputation analysis reveals that the Web sites of the fake and real news publishers exhibit diverse registration behaviors, registration timing, domain rankings, and domain popularity. In addition, fake news tends to disappear from the Web after a certain amount of time. The content characterizations on the fake and real news corpus suggest that simply applying term frequency-inverse document frequency(tf-idf) and Latent Dirichlet Allocation(LDA) topic modeling is inefficient in detecting fake news,while exploring document similarity with the term and word vectors is a very promising direction for predicting fake and real news. To the best of our knowledge, this is the first effort to systematically study domain reputations and content characteristics of fake and real news, which will provide key insights for effectively detecting fake news on social media. 展开更多
关键词 SOCIAL media FAKE NEWS detection CONTENT modeling DOMAIN reputations
有限元法分析髌腱炎状态时的生物力学变化 预览
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作者 周玉 龙小安 +1 位作者 李宁 王纯 《中国组织工程研究》 CAS 北大核心 2020年第8期1280-1286,共7页
背景:对于髌腱炎生物力学的研究利用实验条件获取存在一定的难度,有限元法可以利用其强大的建模及模 拟计算机功能解决实验获取存在的难题。 目的:总结有限元分析在髌腱炎产生机制、治疗方法、膝部可穿戴设备的设计等几个方面的应用,为... 背景:对于髌腱炎生物力学的研究利用实验条件获取存在一定的难度,有限元法可以利用其强大的建模及模 拟计算机功能解决实验获取存在的难题。 目的:总结有限元分析在髌腱炎产生机制、治疗方法、膝部可穿戴设备的设计等几个方面的应用,为髌腱炎 的预防及康复提供理论性指导,并对有限元分析在髌腱炎研究的应用提供新的思路。 方法:第一作者以“有限元分析,髌腱(炎),膝部,生物力学,finite element alaysis,Patellar tendinitis,knee, biomechanics”为检索词,在中国期刊全文数据库(CNKI)、SportDiscus、PubMed 数据库、Elsevier 数据库 中检索 1981 至 2019 年发表的相关文献。 结果与结论:目前各种用于模拟人体生物力学作用机制的模拟分析算法被不断地开发,进而实现对复杂结构 膝部组织及可穿戴设备模型的建立和分析;实现对膝部连续运动状态下非线性的、动态分析,使得模拟分析 的真实度得以提升;利用有限元法进一步进行髌腱炎治疗手段的探索、康复器械的研发、可穿戴设备类整体 材料和结构的设计,都将是今后研究的发展方向。 展开更多
关键词 有限元分析 髌腱炎 生物力学 膝部 可穿戴设备 肌内效贴 组织构建 建模
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Two-dimensional numerical simulation of sediment transport usingimproved critical shear stress methods 预览
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作者 Zhiyong Feng Guangming Tan +3 位作者 Junqiang Xia Caiwen Shu Peng Chen Ran Yi 《国际泥沙研究:英文版》 SCIE 2020年第1期15-26,共12页
Research on the critical shear stresses for erosion and deposition for cohesive sediment has attracted substantial attention from both engineering and theoretical viewpoints due to their importance in sediment transpo... Research on the critical shear stresses for erosion and deposition for cohesive sediment has attracted substantial attention from both engineering and theoretical viewpoints due to their importance in sediment transport theory.Previous studies have proposed a large number of empirical and semiempirical methods to estimate the critical erosion and deposition shear stress,but comparative analyses and validation of the existing methods are still lacking,leaving questions regarding the applicability ranges of the methods.The current paper evaluates the performance and applicability range of five critical erosion shear stress methods derived from different hypotheses on sediment transport for flume experiments and natural tidal rivers using a process-based model.In addition,the effect of the critical deposition shear stress on sediment transport is investigated.The results show that the different critical erosion shear stress methods yield distinctly different prediction results,and their performance and applicability ranges are discussed by comparing their predictions with measured sediment concentrations from the Shenzhen River and measured geometric changes from the Partheniades'flume experiment.The hiding and exposure effect has been recognized as a crucial factor in the incipient motion of sediment on nonuniform beds.A sensitivity analysis of selective deposition and continuous deposition justifies the existence of the critical deposition shear stress.The current study highlights the performance and applicability ranges of the existing critical shear stress methods in sediment transport modeling for uniform and nonuniform beds,which will enrich understanding of the underlying mechanisms of erosion and deposition of cohesive sediment. 展开更多
关键词 Cohesive sediment Critical shear stress Hiding and exposure effect Numerical modeling Shenzhen river
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切段式甘蔗收割机排杂仿真建模方法研究 预览
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作者 郭无极 杨望 +4 位作者 温翔 杨坚 莫建霖 曾伯胜 农宏亮 《农机化研究》 北大核心 2020年第8期6-12,共7页
针对目前切段式甘蔗收割机排杂装置排杂机理研究匮乏的问题,通过SolidWorks和ICEM建立了排杂装置简化的几何模型,对收割机切段后的蔗料进行了分类,并利用EDEM离散元软件进行建模及离散元参数的测定和标定。采用Fluent软件进行了收割机... 针对目前切段式甘蔗收割机排杂装置排杂机理研究匮乏的问题,通过SolidWorks和ICEM建立了排杂装置简化的几何模型,对收割机切段后的蔗料进行了分类,并利用EDEM离散元软件进行建模及离散元参数的测定和标定。采用Fluent软件进行了收割机排杂装置的稳态风场仿真,通过室内试验进行了验证。在此基础上,采用计算流体动力学CFD(Computational Fluid Dynamics)和离散元方法DEM(Discrete Element Method)的耦合方法建立了排杂装置-蔗秆段-蔗尾(碎蔗)-蔗叶的耦合仿真模型,并通过田间试验进行了验证。结果表明:建立的排杂装置-蔗秆段-蔗尾(碎蔗)-蔗叶的耦合系统仿真模型合理,可为进一步研究排杂装置工作机理及优化排杂装置提供参考。 展开更多
关键词 切段式甘蔗收割机 排杂作业 CFD-DEM耦合 仿真 建模
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Recent Progress in Numerical Atmospheric Modeling in China 预览
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作者 Rucong YU Yi ZHANG +4 位作者 Jianjie WANG Jian LI Haoming CHEN Jiandong GONG Jing CHEN 《大气科学进展:英文版》 SCIE CAS CSCD 2019年第9期938-960,共23页
This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011,including the dynamical core,model physics,data assimilation,ensemble forecasting,and model evaluation strategie... This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011,including the dynamical core,model physics,data assimilation,ensemble forecasting,and model evaluation strategies.In terms of the dynamical core,important efforts have been made in the improvement of the existing model formulations and in exploring new modeling approaches that can better adapt to massively parallel computers and global multiscale modeling.With regard to model physics,various achievements in physical representations have been made,especially a trend toward scale-aware parameterization for accommodating the increase of model resolution.In the field of data assimilation,a 4D-Var system has been developed and is operationally used by the National Meteorological Center of China,and its performance is promising.Furthermore,ensemble forecasting has played a more important role in operational forecast systems and progressed in many fundamental techniques.Model evaluation strategies,including key performance metrics and standardized experimental protocols,have been proposed and widely applied to better understand the strengths and weaknesses of the systems,offering key routes for model improvement.The paper concludes with a concise summary of the status quo and a brief outlook in terms of future development. 展开更多
关键词 NUMERICAL MODELING ATMOSPHERIC MODELING WEATHER and CLIMATE MODELING
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Hydric Properties Evolution of <i>Spirulina platensis</i>during Drying: Experimental Analysis and Modeling 预览
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作者 Eloi Salmwendé Tiendrebeogo Guy Christian Tubreoumya +5 位作者 A. O. Dissa A. Compaoré Jean Koulidiati F. Cherblanc J.-C. Bénet I. Youm 《食品与营养科学(英文)》 2019年第6期561-577,共17页
Hydric properties evolution during drying differs from one product to another and has been the subject of various studies due to its crucial importance in modeling the drying process. The variation of these parameters... Hydric properties evolution during drying differs from one product to another and has been the subject of various studies due to its crucial importance in modeling the drying process. The variation of these parameters in the solid matrix and in time during the drying of Spirulina platensis has not known an advanced understanding. The objective of this study was to evaluate the evolution of the water content profile, the mass flow, the concentration gradient and the diffusion coefficient during the drying of Spirulina platensis taking into account the shrinkage. Modeling and experimental analysis (at 50°C and HR = 6%) by the cutting method a cylinder 20 mm in diameter and 40 mm thick were carried. The water content profiles of two different products grown in semi-industrial farms from Burkina Faso and France with initial water contents respectively of the range from 2.73 kgw/kgdb and 3.12 kgw/kgdb were determined. These profiles have been adjusted by a polynomial function. Identical water behavior is observed regardless of the origin of the samples. Water distribution is heterogeneous. Mass flow and concentration gradient are greater at the edge than inside the product. The water transport coefficient, ranging from 1.70 × 10?10 to 94 × 10?10 m2/s, is determined from a linear approach. 展开更多
关键词 DRYING EXPERIMENT Modeling SPIRULINA PLATENSIS Hydric Property
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NaOH Activation of Raw Soils: Effect of NaOH Content on the Drying Kinetic and Its Modelling 预览
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作者 Stevina Bouyila Raymond Gentil Elenga +2 位作者 Louis Ahouet Mondésir Ngoulou Serge Konda 《地质材料(英文)》 2019年第2期55-66,共12页
NaOH activation of soils is an affordable and promising way to improve mechanical properties of earthen bricks. If for well-activated geopolymers, the hard polymeric network limits the influence of water on mechanical... NaOH activation of soils is an affordable and promising way to improve mechanical properties of earthen bricks. If for well-activated geopolymers, the hard polymeric network limits the influence of water on mechanical properties, for the weakly activated one, as non-calcined raw clayey soils, the influence of water on these properties would be more critical. This work aims to determine the effect of sodium hydroxide concentration on the drying kinetics of bricks made with raw clayey soils, and to model this kinetics. The results show that the drying kinetics is governed by the diffusion of water due to the absence of free water. The drying duration increases linearly with the increasing of NaOH content, while the volumetric shrinkage decreases, probably thanks to the reduction of the material porosity during the formation of the zeolitic structures. Besides, the drying duration is strongly and negatively correlated with the initial drying rate (&#8722;0.97) and bricks did not show visible cracks. Among the five parametric models tested, the Khazaei’s model is the best in terms of all statistical criteria considered. For all models used, the coefficient of determination is ranged from 0.993 to 0.999, and the evolution of the models’ parameters is in accordance with that of the drying kinetics observed. 展开更多
关键词 Earthen BRICK Stabilization ALKALINE Activation Modeling GEOPOLYMER DRYING Kinetics
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Efficient multi-response adaptive sampling algorithm for construction of variable-fidelity aerodynamic tables
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作者 Maxim TYAN Jae-Woo LEE 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第3期547-558,共12页
Adaptive sampling is an iterative process for the construction of a global approximation model. Most of engineering analysis tools computes multiple parameters in a single run. This research proposes a novel multi-res... Adaptive sampling is an iterative process for the construction of a global approximation model. Most of engineering analysis tools computes multiple parameters in a single run. This research proposes a novel multi-response adaptive sampling algorithm for simultaneous construction of multiple surrogate models in a time-efficient and accurate manner. The new algorithm uses the Jackknife cross-validation variance and a minimum distance metric to construct a sampling criterion function. A weighted sum of the function is used to consider the characteristics of multiple surrogate models. The proposed algorithm demonstrates good performance on total 22 numerical problems in comparison with three existing adaptive sampling algorithms. The numerical problems include several two-dimensional and six-dimensional functions which are combined into singleresponse and multi-response systems. Application of the proposed algorithm for construction of aerodynamic tables for 2 D airfoil is demonstrated. Scaling-based variable-fidelity modeling is implemented to enhance the accuracy of surrogate modeling. The algorithm succeeds in constructing a system of three highly nonlinear aerodynamic response surfaces within a reasonable amount of time while preserving high accuracy of approximation. 展开更多
关键词 Adaptive sampling Aerodynamic DATABASE Multi-response system Surrogate MODELING VARIABLE FIDELITY MODELING
Modeling and Optimization of Two Clays Acidic Activation for Phosphate Ions Removal in Aqueous Solution by Response Surface Methodology 预览
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作者 Yao Joseph Adjoumani Pierre Jean Marie Richard Dablé +3 位作者 Konan Edmond Kouassi Soumahoro Gueu Alain Stéphane Assémian Kouassi Benjamin Yao 《水资源与保护(英文)》 2019年第2期200-216,共17页
This work deals with phosphate ions removal in aqueous solution by adsorption carried out using two clays, both in activated form. One, non-swelling clay, rich in kaolinite, is associated with illite and quartz. The o... This work deals with phosphate ions removal in aqueous solution by adsorption carried out using two clays, both in activated form. One, non-swelling clay, rich in kaolinite, is associated with illite and quartz. The other, swelling, richer in montmorillonite, is associated with kaolinite, illite and quartz. Seven factors including these two clays were taken into account in a series of experimental designs in order to model and optimize the acidic activation process favoring a better phosphate removal. In addition to the choice of clay nature, the study was also interested in the identification of the mineral acid, between hydrochloric acid and sulfuric acid, which would promote this acidic activation. Response Surface Methodology (RSM) was used for this purpose by sequentially applying Plackett and Burman Design and Full Factorial Design (FD) for screening. Then, a central composite design (CCD) was used for modeling the activation process. A mathematical surface model has been successfully established. Thus, the best acidic activation conditions were obtained by activating the montmorillonite clay with a 2N sulfuric acid solution, in an acid/clay mass ratio of 7.5 at 100°C for 16H. The phosphate removal maximum rate obtained was estimated at 89.32% ± 0.86%. 展开更多
关键词 Clay ACIDIC ACTIVATION MODELING Optimization PHOSPHATE REMOVAL Response Surface Methodology
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Patients Body Modeling: A Practical Theoretical Experience in Plastic Surgery 预览
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作者 José Humberto Cardoso Resende Issacar de Oliveira Costa +7 位作者 Pedro Fernando Huertas Granobles Rolando Arturo Romero Balcazar Guilherme Bahia de Carvalho Hugo Rojas Perdomo Edmar Moreira Lisb?a Mohamad Youssef Mohsen álváro Sanchez Vargas Nébia Maria Almeida de Figueiredo 《现代整形外科(英文)》 2019年第3期52-58,共7页
This research is an active pedagogical experience with surgeons who are specialized in reconstructive plastic surgery and nursing. The guiding questions were the statements of each Surgeon’s clients and what they thi... This research is an active pedagogical experience with surgeons who are specialized in reconstructive plastic surgery and nursing. The guiding questions were the statements of each Surgeon’s clients and what they think about them. Modeling the imaginary bodies of the patients and identify what they built in their minds, highlighting topics and the discussion about the practice made in clay modeling. Eight bodies were modeled, with six bodies with all the senses and two incomplete bodies with only the regions of the breasts and buttocks. It was concluded that there are diverse issues emerging such as gender, ethics, care, spirituality and dream as the fulfillment of the wishes of the patients. Where in the body can these surgeons act to improve the patients’ physical and quality of life? There is an important theme when we are generally welcoming women into an anamnesis that considers their body as a whole, but what is their expectation for each patient? This paper showed the importance of the preoperative evaluation of this whole, for the indication of repairs or contraindications of procedures that aim to improve the physical of the patients, with possible bodily surgical modifications as a form of modeling through liposuction, grafting or excision with lipectomy and withdrawal of excess skin to mitigate the effects of the transformations that deform the physical and end up harming the human relationship, especially women. This is a qualitative method showing the meanings of the bodies of the women represented in the modeling by the Surgeons. However, some surgeons stand out by the look of their practice, as greater sensitivity looking at the body as a whole, spiritual and emotional. They need to use their skills as surgical art and gift, to try to achieve a means, but not an end. 展开更多
关键词 Modeling BODIES SURGERY PLASTIC Art
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Modeling Reforestation’s Role in Climate-Proofing Watersheds from Flooding and Soil Erosion 预览
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作者 Robert L. France Andrew S. M. Patton Peter W. Aitchison 《美国气候变化期刊(英文)》 2019年第3期387-403,共17页
The mitigation potential of reforestation for offsetting the deleterious effects of increased flooding and soil erosion projected to occur in Atlantic Canada through future climate change was investigated. Modelling d... The mitigation potential of reforestation for offsetting the deleterious effects of increased flooding and soil erosion projected to occur in Atlantic Canada through future climate change was investigated. Modelling determined a strong but non-linear relationship between extent of vegetative cover and runoff volume and discharge rate for a Nova Scotian watershed, suggesting that reforestation will reduce, but not completely prevent, flooding. Predicted erosion rates were found to be progressively reduced in relation to the extent of upland reforestation. Of three scenarios examined in which 60%, 65%, and 85% of the entire watershed are randomly reforested, only the latter would reduce the elevated erosion expected to occur through climate change back to present-day existing levels. Additional modelling revealed that comparable mitigation of soil erosion can ensue through implementation of 70 m streamside buffer strips, which would only take up 19% of the total surface area. Prioritizing riparian zones for reforestation will therefore subsume less of the overall productive land area and therefore enact a less severe socio-economic impact on agriculture and forestry. 展开更多
关键词 CLIMATE Change Watersheds MODELING FLOODING Soil Erosion REFORESTATION
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Churn Prediction Using Machine Learning and Recommendations Plans for Telecoms 预览
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作者 Khulood Ebrah Selma Elnasir 《电脑和通信(英文)》 2019年第11期33-53,共21页
Keeping customers satisfied is truly essential for saying that business is successful especially in the telecom. Many companies experience different techniques that can predict churn rates and help in designing effect... Keeping customers satisfied is truly essential for saying that business is successful especially in the telecom. Many companies experience different techniques that can predict churn rates and help in designing effective plans for customer retention since the cost of acquiring a new customer is much higher than the cost of retaining the existing one. In this paper, three machine learning algorithms have been used to predict churn namely, Na?ve Bayes, SVM and decision trees using two benchmark datasets IBM Watson dataset, which consist of 7033 observations, 21 attributes and cell2cell dataset that contains 71,047 observations and 57 attributes. The models’ performance has been measured by the area under the curve (AUC) and they scored 0.82, 0.87, 0.77 respectively for IBM dataset and 0.98, 0.99, 0.98 respectively for cell2cell dataset. The proposed models also obtained better accuracy than the previous studies using the same datasets. 展开更多
关键词 CHURN Prediction TELECOMMUNICATION Modeling Analysis SVM Na?ve BAYES Decision Trees Cell2cell IBM
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Modeling the Drying Kinetics of Earth Bricks Stabilized with Cassava Flour Gel and Amylopectin 预览
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作者 Mondésir Ngoulou Raymond Gentil Elenga +2 位作者 Louis Ahouet Stevina Bouyila Serge Konda 《地质材料(英文)》 2019年第1期40-53,共14页
Earth bricks could contribute to alleviate the housing shortage in the world, thanks to their low cost, easy production, and low environmental impact. However, to manufacture bricks with required properties, many raw ... Earth bricks could contribute to alleviate the housing shortage in the world, thanks to their low cost, easy production, and low environmental impact. However, to manufacture bricks with required properties, many raw soils must be ameliorated. In Central and Eastern Africa, the waste water of the cassava processing is used to improve earth brick mechanical properties. This technique is interesting, because it is sustainable, low-cost and easy to implement. But, studies on this stabilization method are scarce, in particular on the drying kinetics of these bricks. Now, it is important to know the drying duration, because the earth brick’s strength is strongly correlated to its moisture content. Thus, this study aims to quantify and to model the effect of adding cassava flour gel and amylopectin on the drying kinetics of earth bricks. Depending on the soil nature, the drying duration decreases from 7% to 25% for a stabilizer content of 20%. For the five models used, the coefficient of determination is superior to 0.997 and the chi square is inferior to 3 × 10&#8722;4. In average, the best model is Khazaei, followed in order by Avrami-Page, diffusion, Yong and Peleg. The effective coefficient of diffusion of water is about 4 × 10&#8722;5 m&#8901;s&#8722;2. The parameter T of the Khazaei’s model is strongly correlated to the drying duration and the stabilizer content, and their relationships have been deduced. 展开更多
关键词 EARTH BRICK Stabilization Drying Kinetics MODELING CASSAVA Starch
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Response Surface Modeling of Fuel Rich and Fuel Lean Catalytic Combustion of the Stabilized Confined Turbulent Gaseous Diffusion Flames 预览
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作者 Tahani S. Gendy Salwa A. Ghoneim Amal S. Zakhary 《世界工程和技术(英文)》 2019年第1期1-17,共17页
The Response Surface Methodology (RSM) has been applied to explore the thermal structure of the experimentally studied catalytic combustion of stabilized confined turbulent gaseous diffusion flames. The Pt/γAl2O3 and... The Response Surface Methodology (RSM) has been applied to explore the thermal structure of the experimentally studied catalytic combustion of stabilized confined turbulent gaseous diffusion flames. The Pt/γAl2O3 and Pd/γAl2O3 disc burners were situated in the combustion domain and the experiments were performed under both fuel-rich and fuel-lean conditions at a modified equivalence (fuel/air) ratio (&oslash;) of 0.75 and 0.25 respectively. The thermal structure of these catalytic flames developed over the Pt and Pd disc burners were inspected via measuring the mean temperature profiles in the radial direction at different discrete axial locations along the flames. The RSM considers the effect of the two operating parameters explicitly (r), the radial distance from the center line of the flame, and (x), axial distance along the flame over the disc, on the measured temperature of the flames and finds the predicted maximum temperature and the corresponding process variables. Also the RSM has been employed to elucidate such effects in the three and two dimensions and displays the location of the predicted maximum temperature. 展开更多
关键词 Catalytic Combustion FUEL Lean/Fuel RICH NOBLE Metals Burners Thermal Structure Modeling Response Surface Method
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Precise Measurements of the Gravitational Constant: Revaluation by the Information Approach 预览
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作者 Boris Menin 《应用数学与应用物理(英文)》 2019年第6期1272-1288,共17页
The gravitational constant discovered by Newton is still measured with a relative uncertainty that is several orders of magnitude larger than the relative uncertainty of other fundamental constants. Numerous methods a... The gravitational constant discovered by Newton is still measured with a relative uncertainty that is several orders of magnitude larger than the relative uncertainty of other fundamental constants. Numerous methods are used to measure it. This article discusses the information-oriented approach for analyzing the achievable relative measurement uncertainty, in which the magnitude of the gravitational constant can be considered as plausible. A comparison is made and the advantages and disadvantages of various methods are discussed in terms of the possibility of achieving higher accuracy using a new metric called comparative uncertainty, which was proposed by Brillouin. 展开更多
关键词 GRAVITATIONAL CONSTANT Comparative UNCERTAINTY INFORMATION Theory Modeling RELATIVE UNCERTAINTY
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Forecasting Measles Immunization Coverage Using ARIMA Model 预览
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作者 Rachel T. Alegado Gilbert M. Tumibay 《电脑和通信(英文)》 2019年第10期157-168,共12页
This study aimed to find a model to forecast monthly measles immunization coverage using Autoregressive Integrated Moving Average (ARIMA). The monthly registered data for measles immunization coverage from January 201... This study aimed to find a model to forecast monthly measles immunization coverage using Autoregressive Integrated Moving Average (ARIMA). The monthly registered data for measles immunization coverage from January 2014 to December 2018 were used for the development of the model. The best model with the smallest Normalized Bayesian Information Criterion (BIC) of 8.673 is ARIMA (0, 1, 0). ARIMA (0, 1, 0) was used to forecast the monthly measles immunization coverage for the next 36 months from January 2018 to December 2020. The results obtained prove that this model can be used for forecasting future immunization coverage and will help decision-makers to establish strategies, priorities, and proper use of immunization resources. 展开更多
关键词 Forecasting MEASLES IMMUNIZATION COVERAGE ARIMA MODELING
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Land Use Land Cover Change Detection and Deforestation Modeling: In Delomena District of Bale Zone, Ethiopia 预览
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作者 Girma Ayele Hussein Hayicho Mersha Alemu 《环境保护(英文)》 2019年第4期532-561,共30页
Previous studies in Delo-Mena district failed to provide conceptual framework about causes and impacts of deforestation including prediction of spatial location of future deforestation. The study was aimed at investig... Previous studies in Delo-Mena district failed to provide conceptual framework about causes and impacts of deforestation including prediction of spatial location of future deforestation. The study was aimed at investigating spatiotemporal dynamics and prediction of future trends of deforestation in this area. Three periods Landsat images were downloaded and preprocessed using ENVI 4.3. Supervised classification technique was employed for image classification. Land Change Modular used to predict deforestation based on transition between 2000 and 2015 along three driving variables (road distance, settlement and soil). Six land-use land-cover classes were classified for three periods. The result indicated that the forest areas were 91,339, 73,274 and 70,481 hectors in year 2000, 2010 and 2015, respectively. This forest area was reduced by 20% between 2000 and 2010 at annual rate of 2%. Between 2010 and 2015, a forest area was lost by 4% with annual rate of 1%. This deforestation rate was greater than global rates and was lower than rates of south eastern African countries. Farmland expansion was a major cause of deforestation contributed to the annual forest loss by 4.9% and 36% over different periods. In 2030, about 33,243 hectors of a forest area would be expected to disappear that implied emission of about 17 million ton of carbon dioxide. Fuelwoods shortage and loss of biodiversity were perceived as impacts of deforestation. Farm-land and settlement were found increasing at expense of vegetation. Forest plantation, supply of fuel efficient technology and community mobilization were recommended that would be emphasized by the forestry sector based at the district office. 展开更多
关键词 DEFORESTATION LULC MODELING TRANSITIONS Land Change MODULAR
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Insight of surface treatments for CMOS compatibility of InAs nanowi
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作者 Daya S. Dhungana Anne Hemeryck +3 位作者 Nicolo Sartori Pier-Francesco Fazzini Filadelfo Cristiano Sebastien R. Plissard 《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第3期581-586,共6页
A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas ... A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic ann eali ng prior to growth. Morphological and structural characterizati ons of the InAs nano wires are prese nted and growth mecha nisms are discussed in detail. The major in flue nee of surface termi nation is exposed both experime ntally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of I nAs nano wires can be explai ned by these differe nt surfaces termi nations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nano wires (up to 50 nm in diameter and 3 micron in len gth) without passi ng the 410℃ thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface termi nations. 展开更多
关键词 Ⅲ-Ⅴ SEMICONDUCTORS on silicon INAS NANOWIRES self-catalyzed GROWTH hydrogen preparation GROWTH MODELING density functional theory (DFT) MODELING
Artistic Augmentation of Photographs with Droplets
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作者 Mo-Han Zhang Jin-Hui Yu +1 位作者 Kang Zhang Jun-Song Zhang 《计算机科学技术学报:英文版》 SCIE EI CSCD 2019年第6期1294-1306,共13页
Artistic augmentation of photographs with water droplets aims at generating aesthetic yet realistic images, and thus differs from traditional augmented reality in two aspects. One difference lies in the adoption of a ... Artistic augmentation of photographs with water droplets aims at generating aesthetic yet realistic images, and thus differs from traditional augmented reality in two aspects. One difference lies in the adoption of a new image as the environment map in order to render reflected or refracted effects on the surface of inserted water droplets. The other difference is in modeling of water droplets including hanging droplets and resting droplets. These differences raise two research challenges:(1) how to adjust the brightness and colors of the new environment map to maintain visual consistency between the new environment map and the original input image;(2) how to model hanging and resting droplets aesthetically. This paper proposes a framework that addresses these two challenges and demonstrates the effectiveness of our framework by generating example augmented images. 展开更多
关键词 artistic augmentation augmented reality illumination estimation droplet modeling image-based modeling
Numerical Study of Burning of Biomass in Fixed Bed 预览
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作者 Chamga Tchana Armand Obounou Akong Beguide Bonoma 《能源与动力工程(英文)》 2019年第2期35-57,共23页
The combustion of biomass not only falls in energy production, but also in the recovery of waste. The treatment method most used for the recovery of waste is incineration because this method of treatment can minimize ... The combustion of biomass not only falls in energy production, but also in the recovery of waste. The treatment method most used for the recovery of waste is incineration because this method of treatment can minimize the volume of waste. In this work, it comes to realize a numerical modeling of the combustion of biomass in a fixed grate furnace. A literature review allowed us to describe the stages of combustion in terms of mathematical equations. Taking into account the results of elemental analysis and immediate analysis, solid and gaseous species used to simulate their transport equations are: Dry fuel (biomass), char, CH4, O2, CO, H2O, CO2, and N2. From equations of energy transportation, we deducted the TS temperature of the solid fuel bed and Tg of gas. Subsequently, we simulated the resolution 1-D transport equations using a computer code written by us and this on the basis of mathematical modeling of the transport equations. This 1-D unstationnary model takes into account the different stages of load transformation. In this calculation code, we used the explicit Euler method for space discretization, and for the time resolution, we used an implicit method which solves stiff problems of differential equations to ordinary derivatives. The results are satisfactory because the calculated numerical profiles follow the experimental profiles, such as, the temperature profiles, the loss of mass of the fuel bed and the speed of propagation of the flame front. 展开更多
关键词 Multiphasic COMBUSTION BIOMASS Modeling Numerical COMPUTATION Fixed BED
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