Comparison of CAR and VAR Biomass Models

The CAR(Constant Allometric Ratio) and VAR(Variable Allometric Ratio) models wer e two basic biomass models most widely used in research and applications. Re\|sa mpling and sign test were employed in this paper to compare these two models for their parameters' stabilities and their predictions. Research showed that the C AR model would give more stable parameter and more accurate estimation than the VAR model.

Yield Stability of Maize Hybrids Evaluated in National Maize Cultivar Regional Trials in Southwestern China Using Parametric Methods

Assessment of yield stability is an important issue for maize （Zea mays L.） cultivar evaluation and recommendation. Many parametric procedures are available for stability analysis, each of them allowing for different interpretations. The objective of the present study was to assess yield stability of maize hybrids evaluated in the National Maize Cultivar Regional Trials in southwestern China using 20 parametric stability statistics proposed by various authors at different times, and to investigate their interrelationships. Two yield datasets were obtained from the 2003 and 2004 national maize cultivar regional trials in southwestern China. A combined analysis of variance, stability statistics, and rank correlations among these stability statistics were determined. Effects of location, cultivar, and cultivar by location interaction were highly significant （P〈0.01）. Different stability statistics were used to determine the stability of the studied cultivars. Cultivar mean yield （Y） was significantly correlated to the Lin and Binns stability statistic （LP, r=0.98^＊＊ and 0.97^＊＊ for 2003 and 2004 trials, respectively） and desirability index （HD, r=0.38 and 0.84^＊＊ for the 2003 and 2004 trials, respectively）. The statistics LP and HD would be useful for simultaneously selecting for high yield and stability. Based on a principal component analysis, the parametric stability statistics grouped as four distinct classes that corresponded to different agronomic and biological concepts of stability.

ON THE STABILITY OF THE SOLUTION TO A GONORRHEA DISCRETE MATHEMATICAL MODEL

In this paper, the author studies the stability of the solution to a three-dimension-al gonorrhea discrete mathematical model by Liapunoy method. The parameter es-timator of the slability domain is obtained and the rationality of the model is ex-plained in a theoretic way.

Numerical Method for Evaluating Aircraft's Stability Parameters through an Aerodynamic Model

A numerical method is developed to evaluate the dynamic stability parameters of aircraft. This method is based on the aerodynamic model proposed by Etkin. His model is analyzed and generalized. After giving the specific forms of the aerodynamic model, the dynamic stability parameters are determined by the unsteady flow field computation and a parameter identification technique. Numerical experiments show that this method is accurate in predicting the dynamic stability characteristics of blunt cones in hypersonic flight.

Full mode flight dynamics modelling and control of stopped-rotor UAV

The Stopped-Rotor(SR)UAV combines the advantages of vertical take-off and landing of helicopter and high-speed cruise of fixed-wing aircraft.At the same time,it also has a unique aerodynamic layout,which leads to great differences in the control and aerodynamic characteristics of various flight modes,and brings great challenges to the flight dynamics modelling and control in full-mode flight.In this paper,the flight dynamics modelling and control method of SR UAV in full-mode flight is studied.First,based on the typical flight profile of SR UAV when performing missions,using the theory and method of fuzzy mathematics,the T-S flight dynamics model of SR UAV in full-mode flight is established by synthesizing the flight dynamics model of each flight mode.Then,an explicit model tracking and parameter adjusting control system based on fuzzy theory is designed to enhance the stability of the inner loop of SR UAV in full-mode flight,which effectively reduces the coupling between axes and improves the control quality of the system.Finally,the outer loop control system is designed by using classical control method,and the control law of SR UAV in full-mode automatic flight is obtained.The simulation results show that the proposed control system design method is feasible and effective,which lays a solid foundation for the subsequent engineering implementation of the SR UAV.

Grain yield stability analysis using parametric and nonparametric statistics in oat(Avena sativa L.)genotypes in Ethiopia

Background:The performance of oat genotypes differs across environments due to variations in biotic and abiotic factors.Thus,evaluation of oat genotypes across diverse environments is very important to identify superior and stable genotypes for yield improvement.Methods:The study aimed to assess the interaction(genotype-by-environment interaction;GEI)effect and determine the stability of grain yield in oat(Avena sativa L.)genotypes in Ethiopia using parametric and nonparametric stability statistics.Twenty-four oat genotypes were evaluated in nine environments using a randomized complete block design replicated three times.Results:The pooled analysis of the variance of grain yield showed significant variations among genotypes,environments,and their interaction effects.Significant GEI revealed the rank order change of genotypes across environments.The environment main effect captured 44.62%of the total grain yield variance,while genotype and GEI effects explained 28.84%and 26.54%of the total grain yield variance,respectively.The grain yield stability was assessed based on 12 parametric and two nonparametric stability statistics.The results indicated that genotypes with superior grain yield-showed stable performance on the basis of the stability parameters of the genotypic superiority index(P_(i)),the Perkins and Jinks adjusted linear regression coefficient(B_(i)),and the yield stability index(YSI),indicating that selection using these stability parameters would be efficient for grain yield enhancement in oat genotypes.Spearman's rank correlation coefficients also showed that the stability parameters of P_(i),B_(i),and YSI had a significant positive association with grain yield.However,grain yield had an inverse correlation with the stability parameters of standard deviation,deviation from regression (S_(di)^(2)),the Hernandez desirability index(D_(ji)),Wricke ecovalence(W_(i)),the Shukla stability variance(σ_(i)^(2)),the AMMI stability value(ASV),and environmental variance (S_(i)^((2))),indicating that oat genotype selection using these stability parameters would not be efficient for yield enhancement because these stability parameters favor low-yielding genotypes more,compared to high-yielding ones.Conclusions:Therefore,G5,G8,G11,G12,G14,G16,G17,G19,and G22 genotypes were adaptable in all nine environments based on stability parameters of Pi,Bi,and YSI,and selection of these superior genotypes would improve grain yield in oat genotypes.However,the validity of this result should be confirmed by repeating the experiment in the same environments over two or more years.