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Application of a mixed DEA model to evaluate relative efficiency validity 被引量:2
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作者 FU Yu-wei YIN Hang YANG Gui-bin 《Journal of Marine Science and Application》 2005年第3期64-70,共7页
Data envelopment analysis(DEA) model is widely used to evaluate the relative efficiency of producers. It is a kind of objective decision method with multiple indexes. However, the two basic models frequently used at p... Data envelopment analysis(DEA) model is widely used to evaluate the relative efficiency of producers. It is a kind of objective decision method with multiple indexes. However, the two basic models frequently used at present, the C2R model and the C2GS2 model have limitations when used alone,resulting in evaluations that are often unsatisfactory. In order to solve this problem, a mixed DEA model is built and is used to evaluate the validity of the business efficiency of listed companies. An explanation of how to use this mixed DEA model is offered and its feasibility is verified. 展开更多
关键词 decision making units (DMU) efficiency evaluating mixed data envelopment analysis (DEA) model relative efficiency
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Comparison of Two Sample Tests Using Both Relative Efficiency and Power of Test
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作者 Edith Uzoma Umeh Nkiru Obioma Eriobu 《Open Journal of Statistics》 2016年第2期331-345,共15页
This paper, comparison of two sample tests, is motivated by the fact that in the test of significant difference between two independent samples, numerous methods can be adopted;each may lead to significant different r... This paper, comparison of two sample tests, is motivated by the fact that in the test of significant difference between two independent samples, numerous methods can be adopted;each may lead to significant different results;this implies that wrong choice of test statistic could lead to erroneous conclusion. To prevent misleading information, there is a need for proper investigation of some selected methods for test of significant difference between variables/subjects most especially, independent samples. The paper examines the efficiency and sensitivity of four test statistics to ascertain which test performs better. Based on the results, the relative efficiency favours median test as being more efficient than modified median test for both symmetric and asymmetric distributions. In terms of power of test, median test is more sensitive than Modified Median (MMED) test since it has higher power irrespective of the sample sizes for both symmetric and asymmetric distribution. In terms of relative efficiency for asymmetric distribution Modified Mann-Whitney U test is more efficient than Mann-Whitney U test (MMWU), and then for symmetric distribution, Mann-Whitney U test (MMWU) is more efficient than Modified Mann-Whitney in sample size of 5;but for other sample sizes considered Modified Mann-Whitney U test (MMWU) is better than Mann-Whitney. Using power of test for both symmetric and asymmetric distributions, Mann-Whitney is more sensitive than Modified Mann-Whitney U test (MMWU) because it has higher power. 展开更多
关键词 ASYMMETRIC SYMMETRIC Nonparametric Test Two Sample Tests Power of Test relative efficiency
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A new relative efficiency in parameter estimation for linear model
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作者 YANG Hu CHEN Zhu-liang 《Journal of Chongqing University》 CAS 2007年第2期141-145,共5页
A new relative efficiency of parameter estimation for generalized Gauss-Markov linear model was proposed. Its lower bound was also derived. Its properties were explored in comparison with three currently very popular ... A new relative efficiency of parameter estimation for generalized Gauss-Markov linear model was proposed. Its lower bound was also derived. Its properties were explored in comparison with three currently very popular relative efficiencies. The new relative efficiency not only reflects sensitively the error and loss caused by the substitution of the least square estimator for the best linear unbiased estimator, but also overcomes the disadvantage of weak dependence on the design matrix. 展开更多
关键词 linear model: narameter estimation: relative efficiency
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Relative Efficiencies of Optimal Designs in Four Dimensions Constructed Using Balanced Incomplete Block Designs
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作者 Kabue Timothy Gichuki John Gikonyo Kiguta 《Open Journal of Statistics》 2024年第5期439-449,共11页
Experimentally, the best design gives estimates of the desired effects and contrasts with maximum precision. Efficiency as a discriminating factor enables comparison of designs. The goal of Response Surface Methodolog... Experimentally, the best design gives estimates of the desired effects and contrasts with maximum precision. Efficiency as a discriminating factor enables comparison of designs. The goal of Response Surface Methodology (RSM) is the determination of the best settings of the in-put variables for a maximum (or a minimum) response within a region of interest, R. This calls for fitting a model that adequately represents the mean response since such a model, is then used to locate the optimum. D-, A-, E- and T-Optimal designs of a rotatable design of degree two in four dimensions constructed using balanced incomplete block designs (BIBD) when the number of replications is less than three times the number of pairs of treatments occur together in the design and their relative efficiencies to general designs are presented. D-optimal design had 88 runs after replicating the factorial part twice and the axial part thrice with an optimal variance of 0.6965612 giving an efficiency of 97.7% while for A- and T-optimal designs they are formed with 112 runs each obtained by replicating the factorial part two times and axial part six times. Their optimal variances are 0.05798174 and 1.29828 respectively, with efficiency of 71.8% for A-optimal and 87.5% for T-optimal design. E-optimal design was found to be the most efficient design with an only 32 runs comprising only of the factorial part and with an optimal variance of 0.4182000, attaining an efficiency of approximately 1%. This study proposes the adoption of the E-optimal design in estimating the parameters of a rotatable second-order degree model constructed using BIBD for less costs and time saving. 展开更多
关键词 Response Surface Methodology Optimal Designs relative efficiency
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Calculation method of quantum efficiency to TiO_2 nanocrystal photocatalysis reaction 被引量:4
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作者 XIE Yi bing, YUAN Chun wei (National Laboratory of Molecular & Biomolecular Electronics, Southeast University, Nanjing 210096, China.) 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2002年第1期70-75,共6页
The quantum yield is an important factor to evaluate the efficiency of photoreactor. This article gives an overall calculation method of the quantum efficiency( Φ ) and the apparent quantum efficiency( Φ a) to... The quantum yield is an important factor to evaluate the efficiency of photoreactor. This article gives an overall calculation method of the quantum efficiency( Φ ) and the apparent quantum efficiency( Φ a) to the TiO 2/UV photocatalysis system. Furthermore, for the immobility system (IS), the formulation of the faction of light absorbed by the TiO 2 thin film is proposed so as to calculate the quantum efficiency by using the measured value and theoretic calculated value of transmissivity (T). For the suspension system(SS), due to the difficulty to obtain the absorption coefficient ( α ) of TiO 2 particulates, the quantum efficiency is calculated by means of the relative photonic efficiency ( ζ r) and the standard quantum yield ( Φ standard ). 展开更多
关键词 photodegradation reaction quantum efficiency apparent quantum efficiency photonic efficiency relative photonic efficiency absorption coefficient
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Axial response and material efficiency of tapered helical piles 被引量:4
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作者 Hamid Mortazavi Bak Amir M.Halabian +1 位作者 Hamid Hashemolhosseini Mohammadali Rowshanzamir 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2021年第1期176-187,共12页
Different techniques have been proposed to increase the bearing capacity of open-ended piles.Welding helices to the shaft and tapering the pile shaft could be used simultaneously to enhance the static and dynamic beha... Different techniques have been proposed to increase the bearing capacity of open-ended piles.Welding helices to the shaft and tapering the pile shaft could be used simultaneously to enhance the static and dynamic behaviors of these piles.This paper subjects the bearing capacity,stiffness,frictional behavior,and material efficiency of the tapered helical piles to scrutiny.Tapered helical piles are introduced herein as an alternative option to improve the material efficiency of hollow piles.Based on the Taguchi method,a series of experiments was designed and conducted.The axial responses of tapered helical piles are also investigated using finite element analyses.The results derived from loadedisplacement curves and strain gages are used to characterize the axial compression responses of tapered helical piles.The effects of tapered angle,helices diameter and helices distance are examined using dimensionless parameters,and the degree of contribution of these factors is calculated on each of the enumerated variables individually.Experimental results show that the shaft friction resistance of tapered helical piles increases continuously with the pile head settlement.Furthermore,the effect of tapered wall on the shaft friction resistance is more tangible at low stress levels.The results showed that the relative material efficiency factor of the optimum pile could be 2.5 times that of unoptimized pile with a similar quantity of material. 展开更多
关键词 Tapered helical pile Axial response Bearing capacity Shaft resistance Initial tangent stiffness relative material efficiency Taguchi method
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Efficiency Rankings of MBA Programs in Indian Top Public Colleges 被引量:3
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作者 Patrick Jaska Vedamuthu Kulandai Swamy 《Journal of Modern Accounting and Auditing》 2013年第9期1275-1279,共5页
This study examines the relative efficiency of the top 20 Indian public colleges that offer MBAs. These colleges were chosen from a list provided by Careers 360, a magazine in India known for its university rankings. ... This study examines the relative efficiency of the top 20 Indian public colleges that offer MBAs. These colleges were chosen from a list provided by Careers 360, a magazine in India known for its university rankings. The purpose of this study was to evaluate the colleges on an efficiency basis rather than on a total score ranking scale as is the common practice of most publications that rank universities or programs. The ranking method used in this study is based on data envelopment analysis (DEA), a nonparametric procedure for evaluating entities based upon examining inputs in relation to outputs achieved. The rankings using DEA were somewhat different than those given by Careers 360. The results of the DEA analysis of this study rank the universities that are the most efficient at getting students the best salaries and return on investment (ROI) based on the inputs of diversity, work experience, and residency. The authors conclude, as previous studies have shown, that DEA analysis is a useful and non-biased method of comparing university programs. 展开更多
关键词 aniversity academic rankings relative efficiency data envelopment analysis (DEA)
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A Novel High Spectral Efficiency Waveform Coding-OVFDM 被引量:2
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作者 LI Daoben 《China Communications》 SCIE CSCD 2015年第2期61-73,共13页
Based on the Overlapped Multiplexing Principle[12],a frequency domain OVFDM(Overlapped Frequency Domain Multiplexing) Coding is proposed.By the data weighted shift overlapped version of any band-limited Multiplexing T... Based on the Overlapped Multiplexing Principle[12],a frequency domain OVFDM(Overlapped Frequency Domain Multiplexing) Coding is proposed.By the data weighted shift overlapped version of any band-limited Multiplexing Transfer Function H(f) the coding gain and spectral efficiency are both achieved.The heavier the overlap of the data weighted Multiplexing Transfer Function H(f),the higher the coding gain and spectral efficiency as well as the closer the output to the optimum complex Gaussian distribution.The bit error probability performance is estimated.The time domain OVTDM(Overlapped Time Domain Multiplexing) Coding,the dual of OVFDM in time domain is incidentally proposed as well.Both theoretical analysis and testified simulations show that OVFDM(OVTDM) is suitable for high spectral efficiency application and its spectral efficiency is only roughly linear to SNR rather than the well-known logarithm to SNR. 展开更多
关键词 overlapped multiplexing principle frequency domain coding waveform coding spectral efficiency shannon capacity dual relation OVFDM OVTDM
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THE INEFFICIENCY OF THE LEAST SQUARES ESTIMATOR AND ITS BOUND
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作者 杨虎 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1990年第11期1087-1093,共7页
It was suggested by Pantanen that the mean squared error may be used to measure the inefficiency of the least squares estimator. Styan[2] and Rao[3] et al. discussed this inefficiency and it's bound later. In this... It was suggested by Pantanen that the mean squared error may be used to measure the inefficiency of the least squares estimator. Styan[2] and Rao[3] et al. discussed this inefficiency and it's bound later. In this paper we propose a new inefficiency of the least squares estimator with the measure of generalized variance and obtain its bound. 展开更多
关键词 inefficiency relative efficiency mean squared error generalized variance matrix derivative best linear unbased estimator
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Experimental Study to Improve the Agronomic Efficiency of Low Grade Fine Size Rock Phosphate
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作者 Mahesh Ganesa Pillai Sumedh Sudhir Beknalkar Saket Sanjay Kashettiwar 《Journal of Agricultural Science and Technology(B)》 2013年第11期783-788,共6页
Soluble phosphate fertilizers have been preferably used in plant crop production. The cost of applying conventional water soluble phosphate fertilizer is high in developing countries since their manufacturing requires... Soluble phosphate fertilizers have been preferably used in plant crop production. The cost of applying conventional water soluble phosphate fertilizer is high in developing countries since their manufacturing requires importing high grade rock phosphate (RP). As a result, the use of indigenously available low-grade RP is gaining importance globally. In this study, experiments were carried out using clayey loamy alkaline soil to evaluate the agronomic efficiency of fine sized low grade RP with inorganic nitrogen fertilizers and it was further compared with that of soluble phosphate fertilizer (di-ammonium phosphate), Cicer arietinum was the test crops subjected to treatments of absolute control, di-ammonium phosphate and low grade RP with varying concentrations of ammonium sulphate or ammonium nitrate. The experiments were conducted during 2012-2013 in the bid to study the growth rate and the biomass of the crop. Tests were also performed to determine the residual effects of the fertilizers on the crops. The results revealed that the combined use of low grade RP and ammonium sulphate or ammonium nitrate, at 16 kg N/ha, resulted in an agronomic efficiency, in terms of biomass of plants, comparable to that of di-ammonium phosphate and was found to be a more attractive management option for resource-poor farmers. 展开更多
关键词 Low grade RP FERTILIZER di-ammonium phosphate residual test relative agronomic efficiency.
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Potassium accumulation and translocation a mongrice genotypes in relation to internal potassium use efficiency(IKUE)
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作者 LIU Jianxiang YANG Xiao’e Wu Lianghuan YANG Yu’ai College of Environmental and Resource Sciences,Zhejiang Univ,Hangzhou 310029,China 《Chinese Rice Research Newsletter》 2001年第1期10-11,共2页
Abiotie stresses including potassium deficiency are limitingfactors for increasing rice yield.Nine rice genotypes(Oryza Sativa L.,indica)differing in sensitivity to low Kstress selected from 200 volume-solution screen... Abiotie stresses including potassium deficiency are limitingfactors for increasing rice yield.Nine rice genotypes(Oryza Sativa L.,indica)differing in sensitivity to low Kstress selected from 200 volume-solution screening wereused in this study to examine accumulation and transloca-tion ofK.The powdery-muddy paddy soil tested contained 30.6mg·kgavailable K(1 N NHAcO extracted),1.92% 展开更多
关键词 IKUE Potassium accumulation and translocation a mongrice genotypes in relation to internal potassium use efficiency than
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The Asynchronous Phenomenon and Relative Efficiency of Tourism Resources in China Based on Panel Data for 31 Provinces from 2001 to 2009 被引量:4
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作者 方叶林 黄震方 +2 位作者 张宏 彭倩 陆玮婷 《Journal of Resources and Ecology》 CSCD 2014年第3期280-288,共9页
We used panel data for 31 Chinese provinces from 2001 to 2009 and entropy methods to evaluate regional tourism resources endowment.Combined with regional tourism revenue,we constructed an asynchronous index and quanti... We used panel data for 31 Chinese provinces from 2001 to 2009 and entropy methods to evaluate regional tourism resources endowment.Combined with regional tourism revenue,we constructed an asynchronous index and quantitatively evaluated every area's asynchronous phenomenon regarding tourism resources.We found that Chinese mainland tourism resources have asynchronous phenomenon: tourism is positively asynchronous in the east(Yangtze River Delta,Pearl River Delta and Beijing-Tianjin region) and negatively asynchronous in central and western China.The total efficiency of tourism resources in eastern China is mainly driven by pure technology efficiency and by scale efficiency in western China.In addition to some provinces,the ranking of provincial total efficiency and the asynchronous index has a strong positive correlation.We conclude with several suggestions for the development of tourism resources across China. 展开更多
关键词 tourism resources asynchronous index relative efficiency entropy-value method superiority degree China
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Estimation of Turbulent Fluxes Using the Flux-Variance Method over an Alpine Meadow Surface in the Eastern Tibetan Plateau 被引量:11
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作者 WANG Shaoying ZHANG Yu +2 位作者 LU Shihua LIU Heping SHANG Lunyu 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2013年第2期411-424,共14页
The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency am... The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles (active or passive) of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones. 展开更多
关键词 flux-variance method relative transfer efficiency eddy-covariance method homogeneous landsurface turbulent flux
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Frontier Analysis of Nepalese Commercial Banks: DEA Approach 被引量:1
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作者 Sunity Shrestha Hada Govinda Tamang 《Journal of Mathematics and System Science》 2014年第10期675-682,共8页
The efficiency of any organizations at manufacturing sector or service sector, profit making or non-profit making, is most important factor for survival and growth of the organization. The Data Envelopment Analysis (... The efficiency of any organizations at manufacturing sector or service sector, profit making or non-profit making, is most important factor for survival and growth of the organization. The Data Envelopment Analysis (DEA) technique is one of the most popular and effective tool to measure relative efficiency hence is appropriate to make comparison among similar organizations with multiple output and input. This study performs frontier analysis and measures the relative efficiency of Nepalese commercial banks using DEA approach with two output and two input variables. 展开更多
关键词 Data envelopment analysis frontier analysis commercial banks relative efficiency
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LIMITING BEHAVIOR OF RECURSIVE M-ESTIMATORS IN MULTIVARIATE LINEAR REGRESSION MODELS AND THEIR ASYMPTOTIC EFFICIENCIES
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作者 缪柏其 吴月华 刘东海 《Acta Mathematica Scientia》 SCIE CSCD 2010年第1期319-329,共11页
Recursive algorithms are very useful for computing M-estimators of regression coefficients and scatter parameters. In this article, it is shown that for a nondecreasing ul (t), under some mild conditions the recursi... Recursive algorithms are very useful for computing M-estimators of regression coefficients and scatter parameters. In this article, it is shown that for a nondecreasing ul (t), under some mild conditions the recursive M-estimators of regression coefficients and scatter parameters are strongly consistent and the recursive M-estimator of the regression coefficients is also asymptotically normal distributed. Furthermore, optimal recursive M-estimators, asymptotic efficiencies of recursive M-estimators and asymptotic relative efficiencies between recursive M-estimators of regression coefficients are studied. 展开更多
关键词 asymptotic efficiency asymptotic normality asymptotic relative efficiency least absolute deviation least squares M-ESTIMATION multivariate linear optimal estimator reeursive algorithm regression coefficients robust estimation regression model
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Highly efficient electrochemiluminescence of nitrogen-doped carbon quantum dots 被引量:1
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作者 Xiaoli Qin Congyang Zhang +8 位作者 Zackry Whitworth Ziying Zhan Kenneth Chu Ping Hu Sara Jahanghiri Jigang Zhou Jinxing Chen Qiao Zhang Zhifeng Ding 《Advanced Sensor and Energy Materials》 2023年第3期2-8,共7页
Nitrogen-doped carbon quantum dots(N-CQDs)are nanocomposites that can be synthesized by the hydrothermal method.In this work,N-CQDs with the size of 3.2±1.7 nm was prepared from 1 g citric acid and 2 g urea precu... Nitrogen-doped carbon quantum dots(N-CQDs)are nanocomposites that can be synthesized by the hydrothermal method.In this work,N-CQDs with the size of 3.2±1.7 nm was prepared from 1 g citric acid and 2 g urea precursor in 10 mL water.Electrochemiluminescence(ECL)of the prepared N-CQDs with K2S2O8 as a coreactant was found to reach a high ECL efficiency up to 109%relative to that of the Ru(bpy)_(3)^(2+)/K_(2)S_(2)O_(8),coreactant system,revealing their great potential for electroanalysis.It is probably because that N elements were doped well in this N-CQDs and increased presence of surface states per mass of N-CQDs.From the spooling ECL spectroscopy,it can be found that the ECL spectra exhibited both a red shift compared with their photoluminescence(PL)spectrum and a wavelength shift during the potentiodynamic scan in the ECL evolution and devolution processes,due to various emissive excited states of N-CQDs leading to higher ECL efficiency.This work gives an insight into development of high ECL efficiency N-CQDs for bioanalytical and light emitting applications. 展开更多
关键词 Nitrogen-doped carbon quantum dots(N-CQDs) Electrochemiluminescence(ECL) Spooling ECL spectroscopy relative ECL efficiency Persulfate coreactant
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Agronomic and Economic Potential of Tughutu and Minjingu Phosphate Rock as Alternative Phosphorus Sources for Bean Growers
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作者 P.A.NDAKIDEMI 《Pedosphere》 SCIE CAS CSCD 2007年第6期732-738,共7页
On-farm experiments were conducted in farmers' fields at 6 different sites in Western Usambara Mountains(WUM)in northern Tanzania during the 2000-2001 cropping season.The objectives were to study the effects of Tu... On-farm experiments were conducted in farmers' fields at 6 different sites in Western Usambara Mountains(WUM)in northern Tanzania during the 2000-2001 cropping season.The objectives were to study the effects of Tughutu(Vernonia subligera O.Hoffn)pruning in combination with Minjingu phosphate rock(MPR)or triple super phosphate(TSP)supply on the concentration of P in the tissues and seed yields of common bean,and to assess the economic returns of these different technologies to farmers.The experimental design was a randomized complete block with each of the 6 farmers' fields used as a replicate.The treatments included:control,MPR or TSP each at 26 kg P ha^(-1),Tughutu at 2.5 t ha^(-1), and Tughutu at 2.5 t ha^(-1)combined with MPR or TSP at 26 kg P ha^(-1). Addition of MPR or TSP alone significantly raised P concentration in bean shoots from 1.27 mg g^(-1)to 1.70 and 1.95 mg g^(-1)respectively.Combining MPR or TSP with Tughutu increased P concentration above the proposed deficiency level of 2 mg g^(-1).The relative agronomic effectiveness(RAE)of MPR ranged from 12.5% to 45.0%.Seed yields of common bean was markedly increased by 28%-104% from MPR or TSP supply alone,and 148%-219% from Tughutu application combined with 26 kg P ha^(-1)of MPR or TSP relative to the control.With Tughutu alone,seed yield increased by 53%. From economic analysis,the increase in seed yield with the supply of MPR or TSP combined with Tughutu translated into a significantly(P≤0.001)higher marginal rate of return and dollar profit for common bean farmers in WUM in northern Tanzania.It is concluded that Tughutu and its combined application with MPR or TSP is an appropriate integrated nutrient management strategy that may increase bean yields and dollar profit to the rural poor communities in Tanzania. 展开更多
关键词 integrated nutrient management marginal rate of return P concentration PROFIT relative agronomic efficiency
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Discussion of the Fluid Acceleration Quality of a Ducted Propulsion System on the Propulsive Performance
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作者 Jui-Hsiang Kao Yi-Fan Liao 《Computer Modeling in Engineering & Sciences》 SCIE EI 2022年第3期1325-1348,共24页
This paper focuses on the ducted propulsion with the accelerating nozzle,and discusses the influence of its fluid acceleration quality on its propulsive performances,including the hull efficiency,the relative rotative... This paper focuses on the ducted propulsion with the accelerating nozzle,and discusses the influence of its fluid acceleration quality on its propulsive performances,including the hull efficiency,the relative rotative efficiency,the effective wake,and the thrust deduction factor.An actual ducted propulsion system is used as an example for computational analysis.The computational conditions are divided into four combinations,which are provided with different propeller pitches,cambers,and duct lengths.Themethod applied in this study is the Computational Fluid Dynamics(CFD)technology,and the contents of the calculation include the hull’s viscous resistance,the wave-making resistance,the propeller performance curve,and the self-propulsion simulation in order to obtain the ship’s effective wake,thrust deduction factor,hull efficiency,and relative rotative efficiency.The performance curve of the propeller and resistance estimation results are compared with the experimental values for determining the correctness of the self-propulsion simulation.According to the computational analysis,it is known that increasing the propeller pitch cannot effectively increase the hull efficiency.The duct acceleration quality can be reduced by shortening the duct length;hence,when the effective wake fraction and thrust deduction factor decrease,the hull efficiency is increased.In addition,the pressure inside the duct is relatively low if the acceleration quality of the duct is too high,which is unfavorable for controlling the propeller cavitation.Moreover,if the hull bottom in front of the propeller is tapered up from the front to the back at an overly steep angle,the thrust deduction factor will be too large and lead to a relatively low hull efficiency. 展开更多
关键词 Ducted propellers accelerating nozzle hull efficiency relative rotative efficiency effective wake thrust deduction factor
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Estimation of scale parameters of logistic distribution by linear functions of sample quantiles
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作者 Patrick G +3 位作者 O WEKE 王承官 吴从炘 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2001年第4期380-382,共3页
The large sample estimation of standard deviation of logistic distribution employs the asymptotically best linear unbiased estimators based on sample quantiles. The sample quantiles are established from a pair of sing... The large sample estimation of standard deviation of logistic distribution employs the asymptotically best linear unbiased estimators based on sample quantiles. The sample quantiles are established from a pair of single spacing. Finally, a table of the variances and efficiencies of the estimator for 5≤n≤65 is provided and comparison is made with other linear estimators. 展开更多
关键词 order statistics logistic distribution quantile estimation relative efficiencies.
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MATRIX NORM VERSIONS OF THE KANTOROVICH INEQUALITY AND ITS APPLICATIONS
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作者 YANG HU 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 1995年第2期133-140,共8页
In this paper we discuss the generalizations of the Kaotorovich inequality and obtain some generalized Kantorovich inequalities in the sense of matrix norm. We further illustrate how to use these inequalities to deter... In this paper we discuss the generalizations of the Kaotorovich inequality and obtain some generalized Kantorovich inequalities in the sense of matrix norm. We further illustrate how to use these inequalities to determine the lower bound of relative efficiency of the parameter estimate in linear model. 展开更多
关键词 Condition number singular value decomposition orthogonal invariant norm relative efficiency.
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