A COMBINED VERIFICATION METHOD FOR PREDICTABILITY OF PERSISTENT HEAVY RAINFALL EVENTS OVER EAST ASIA BASED ON ENSEMBLE FORECAST

Persistent Heavy Rainfall(PHR)is the most influential extreme weather event in Asia in summer,and thus it has attracted intensive interests of many scientists.In this study,operational global ensemble forecasts from China Meteorological Administration(CMA)are used,and a new verification method applied to evaluate the predictability of PHR is investigated.A metrics called Index of Composite Predictability(ICP)established on basic verification indicators,i.e.,Equitable Threat Score(ETS)of 24 h accumulated precipitation and Root Mean Square Error(RMSE)of Height at 500 h Pa,are selected in this study to distinguish"good"and"poor"prediction from all ensemble members.With the use of the metrics of ICP,the predictability of two typical PHR events in June 2010 and June 2011 is estimated.The results show that the"good member"and"poor member"can be identified by ICP and there is an obvious discrepancy in their ability to predict the key weather system that affects PHR."Good member"shows a higher predictability both in synoptic scale and mesoscale weather system in their location,duration and the movement.The growth errors for"poor"members is mainly due to errors of initial conditions in northern polar region.The growth of perturbation errors and the reason for better or worse performance of ensemble member also have great value for future model improvement and further research.

Visual Passive Ranging Method Based on Re-entrant Coaxial Optical Path and Experimental Verification

To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coaxial optical path is presented. The target image is obtained using double cameras with coaxial optical path. Since there is imaging optical path difference between the cameras, the images are different. In comparison of the image differences, the target range could be reversed. The principle of the ranging method and the ranging model are described. The relationship among parameters in the ranging process is analyzed quantitatively. Meanwhile,the system composition and technical realization scheme are also presented. Also, the principle of the method is verified by the equivalent experiment. The experimental results show that the design scheme is correct and feasible with good robustness. Generally, the ranging error is less than 10% with good convergence. The optical path is designed in a re-entrant mode to reduce the volume and weight of the system. Through the coaxial design,the visual passive range of the targets with any posture can be obtained in real time. The system can be widely used in electro-optical countermeasure and concealed photoelectric detection.

Verification test on an innovated method for the studies on inheritance of resistance to rice sheath blight

We have recently developed a systematic method for the study on the inheritance of resistance to sheath blight. The key of the system is an innovated method of inoculation and investigation along with the employment of the permanent population. This paper reported the procedure of the system and the result of its verification.

Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

SCATTERING OF A GRAZING LONGITUDINAL WAVE PULSE BY A RIBBON-TYPE CRACK—EXPERIMENTAL VERIFICATION BY THE PHOTOELASTIC METHOD

By using the dynamic photoelastic method and our technique of fabricating an internal crack in solid , the scattered waves of incident grazing longitudinal ultrasonic wave pulse by a ribbon-type crack are ob-served and analyzed . In particular, the distribution of the intensity of the scattered head wave is measured quantitatively . The experimental results fairly agree with the theoretical ones given in ref. [ 1 ] .

Design and performance analysis of indoor calibration device for the forcemeasuring system of the tractor three-point hitch

The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.

Assessing Hourly Precipitation Forecast Skill with the Fractions Skill Score

Statistical methods for category（yes/no） forecasts, such as the Threat Score, are typically used in the verification of precipitation forecasts. However, these standard methods are affected by the so-called ＂double-penalty＂ problem caused by slight displacements in either space or time with respect to the observations. Spatial techniques have recently been developed to help solve this problem. The fractions skill score（FSS）, a neighborhood spatial verification method, directly compares the fractional coverage of events in windows surrounding the observations and forecasts.We applied the FSS to hourly precipitation verification by taking hourly forecast products from the GRAPES（Global/Regional Assimilation Prediction System） regional model and quantitative precipitation estimation products from the National Meteorological Information Center of China during July and August 2016, and investigated the difference between these results and those obtained with the traditional category score. We found that the model spin-up period affected the assessment of stability. Systematic errors had an insignificant role in the fraction Brier score and could be ignored. The dispersion of observations followed a diurnal cycle and the standard deviation of the forecast had a similar pattern to the reference maximum of the fraction Brier score. The coefficient of the forecasts and the observations is similar to the FSS; that is, the FSS may be a useful index that can be used to indicate correlation.Compared with the traditional skill score, the FSS has obvious advantages in distinguishing differences in precipitation time series, especially in the assessment of heavy rainfall.

Model checking with fairness assumptions using PAT

Recent development on distributed systems has shown that a variety of fairness constraints （some of which are only recently defined） play vital roles in designing self- stabilizing population protocols. Existing model checkers are deficient in verifying the systems as only limited kinds of fair- ness are supported with limited verification efficiency. In this work, we support model checking of distributed systems in the toolkit PAT （process analysis toolkit）, with a variety of fairness constraints （e.g., process-level weak/strong fairness, event-level weak/strong fairness, strong global fairness）. It performs on-the-fly verification against linear temporal prop- erties. We show through empirical evaluation （on recent pop- ulation protocols as well as benchmark systems） that PAT has advantage in model checking with fairness. Previously un- known bugs have been revealed against systems which are designed to function only with strong global fairness.