拉伸试验测量不确定度评定

[目的]根据GB/T5481-2000《检测和校准实验室能力的通用要求》规定,评定实验室拉伸试验测量过程中的不确定度。[方法]按照JJF1059-1999《测量不确定度评定与表示》的方法,按照建立数学模型、分析不确定度的步骤,给出了本实验室拉伸试验不确度度评定的过程。同时讨论了对拉伸试验不确定度评定的结果有较大影响的一些因素。[结果]给出了拉伸试验测量过程中强度和伸长率不确定度评定公式,同时指出了影响公式计算结果的其他因素和进一步的研究方向。

An Uncertainty Assessment Approach for Measuring Flatness Error in Close Way

It is necessary for precise measurement to estimate the uncertainty of measurement result. When measuring flatness error in close way by pitch, usually the uncertainty of measurement result is independently estimated according to pitch points. By analyzing a concrete example, this paper proposed that the uncertainty should be evaluated by the correlation calculating method. This approach greatly improved the deficiencies of the assessment method according to independent measurement and enhanced measurement precision. It provides a reference value for uncertainty assessment in leveling a flat.

Soil Organic Carbon Density in Hebei Province, China: Estimates and Uncertainty

In order to improve the precision of soil organic carbon (SOC) estimates, the sources of uncertainty in soil organic carbon density (SOCD) estimates and SOC stocks were examined using 363 soil profiles in Hebei Province, China, with three methods: the soil profile statistics (SPS), GIS-based soil type (GST), and kriging interpolation (KI). The GST method, utilizing both pedological professional knowledge and GIS technology, was considered the most accurate method of the three estimations, with SOCD estimates for SPS 10% lower and KI 10% higher. The SOCD range for GST was 84% wider than KI as KI smoothing effect narrowed the SOCD range. Nevertheless, the coefficient of variation for SOCD with KI (41.7%) was less than GST and SPS. Comparing SOCD’s lower estimates for SPS versus GST, the major sources of uncertainty were the conflicting area of proportional relations. Meanwhile, the fewer number of soil profiles and the necessity of using the smoothing effect with KI were its sources of uncertainty. Moreover, for local detailed variations of SOCD, GST was more advantageous in reflecting the distribution pattern than KI.

Psychometric properties of the Chinese version of the Parent Perception of Uncertainty Scale(PPUS)among parents of children with cancer diagnosis

Objective:Parents of children diagnosed with cancer often experience high levels of illness uncertainty.This study evaluated the psychometric properties of the Chinese Version of the Parent Perception of Uncertainty Scale for Childhood Cancer(PPUS-CC)in China's Mainland.Methods:Exploratory factor analysis(EFA)and confirmatory factor analysis(CFA)were performed using study population of 420 parents.The participants were also given the social support questionnaire and assessed using the Self-Rating Anxiety Scale,Zarit Burden Interview,and Self-Rating Depression Scale to test the association with PPUS-CC and obtain the cut-off of the scale.Results:The Chinese version of PPUS-CC includes 14 items,and two factors were extracted by EFA,which could explain the 54.56%variances.The Cronbach'sαof two factors ranged from 0.830 to 0.877.The dimensions of PPUS-CC show statistical association with other scales,and the cut-off is 42.5.Conclusion:The Chinese version of PPUS-CC,as a reliable,valid,and easy-to-use clinical tool,can be adapted in clinical settings as a screening tool to recognize parents with high-risk psychological problems.

Uncertainty analysis of ship model vertical center of gravity and transverse moment of inertia test

The usability of test results of ship model vertical center of gravity and transverse moment of inertia is generally depends on its uncertainty. Referring to the guidelines for uncertainty analysis in examination of liquid dynamic recommended by International Towing Tank Conference （ ITTC）, the results were analyzed, bias limits and precision limits were calculated and total uncertainty was estimated. The total uncertainty of six tests on ship model vertical center of gravity is is 0. 16% of the mean value, and the total uncertainty of six tests on ship model transverse moment of inertia is 5.66% of the mean value. The test results show that the total uncertainty of both the multiple tests and the single test is from the precision limits of ship model vertical center of gravity and transverse moment of inertia tests. Thus, the improved measurement system stability can enormously decrease the total uncertainty of multiple tests and the single test.

Uncertainty Calculation of Roundness Assessment by Automatic Differentiation in Coordinate Metrology

Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to the Expression of Uncertainty in Measta- meat （GUM）, all measurement results must have a stated uncertainty associated the titan. However, no CMMs give the uncertainty value of the roundness, because no suitable measrement uncertainty calculation procedure exists. In the case of roundness raeasurement in coordinate metrology, this paper suggests the algorithms for the calculation of the measurement uncertainty of the roudness deviation based on the two mainly used association criteria, LSC and MZC. The calculation of the sensitivity coefficients for the uncertainty calculatiion can be done by autnatic differentiation, in order to avoid introducing additional emars by the traditional difference quotient approxima- tions. The proposed methods are exact and need input data only as the nrasured coordinates of the data points and their associated un- certainties.

Spectrophotometer standardization in UV-Vis spectral region

Ultraviolet-visible（UV-Vis）spectrophotometry is commonly used in analytical laboratories for qualitative and quantitative analyses.To make the data obtained reliable,an experimental instrument must be calibrated.National Institute for Standards（NIS）in Egypt builds up aphotometric method to ensure the competence of absorbance and transmittance to the standard international and national requirements.This paper presents an instrument for UV-Vis measurement,discusses the factors affecting measurement reliability and estabishes the uncertainty model including correspoding measurement parameters.

Realization of Relative Humidity Scale Using NIS Two-Temperature Humidity Generator

A new humidity calibration facility using a 2-T （two-temperature）, constant pressure principle for generating gas of known humidity has been developed at NIS for primary realization of relative humidity scale in the range from 13% to 98% for calibrating and testing hygrometers to improve the uncertainty. This paper reports the construction of the 2-T humidity generator describing its saturator and the test chamber system. Results of the efficiency tests of its saturator showed satisfactory generation performance for a primary realization of relative humidity scale. The expanded uncertainty of the relative humidity with a coverage factor k = 2 was found to be from ± 0.25 % to ± 0.67%.

Impact of Departure Time Uncertainty on Runway Scheduling

The flight departure process is affected by various uncertain factors,such as flight delays,scheduling delays and taxi time etc. A reliable and robust departure sequence is very important to the safe and efficient operation for airports. An optimal scheduling model for multi-runway departure considering the arrival aircraft crossing departure runway is developed. A genetic algorithm encoding flight numbers is designed to find a near-optimal solution. After that,further establish a multi-objective dynamic scheduling model and design a hybrid algorithm to solve it,and compare and analyze the results of the two models. A quantitative analysis of departure time based on the kernel density estimation is performed,and Monte Carlo simulations are carried out to explore the impact of flight departure time’s uncertainty on departure scheduling. The results based on historical data from Guangzhou Baiyun Airport are presented,showing the advantage of the proposed model and algorithm.

Development of NIS Two-Temperature Humidity Generator

Abstract： This paper describes the development and characterization of a two-temperature （2-T）, constant pressure humidity generator It relies on the saturation of a stream of gas flowing over a water surface maintained at constant, well-known, temperature. It was built in order to improve the uncertainties of the dew-point temperature and humidity scales realization at the National Institute for Standard （NIS） in the dew-point range from -50 ℃ to ＋ 10 ℃. Several experiments were carried out in the above mentioned range in order to characterize the generator. Characterization comprised studies of its saturator efficiency, temperature stability and a comparison with a calibrated chilled-mirror hygrometer. The results of the efficiency tests showed good performance of the generator as described below. For uncertainty of measurements, a thorough analysis was also described representing estimations of contributions for all the sources that affecting measurements.

Uncertainty in projections of the South Asian summer monsoon under global warming by CMIP6 models:Role of tropospheric meridional thermal contrast

Driven by the increase in CO_(2)concentration,climate models reach a consensus that the large-scale circulation of the South Asian summer monsoon(SASM) becomes weakened but with different magnitudes.This study investigates the major uncertainty sources of the SASM response to an abrupt quadrupling of CO_(2)(abrupt-4×CO_(2))in 18 models of phase 6 of the Coupled Model Intercomparison Project.The projected weakening of the SASM indicated by both zonal and meridional monsoon circulation indices is closely linked to decreases in the meridional gradient of upper-tropospheric temperature between Eurasia and the Indian Ocean(EUTT-IUTT).A climate feedback-response analysis method is applied to linearly decompose the uncertainty of changes in EUTT-IUTT into the partial changes due to external forcing and internal processes of the earth-atmosphere column.Results show that the uncertainty of changes in EUTT-IUTT is contributed positively by the dominant atmospheric dynamic process,followed by the cloud shortwave radiative effect,and negatively by the surface latent heat flux and cloud longwave radiative effect.Contributions from CO_(2)forcing and other internal processes including albedo and water vapor feedbacks,oceanic heat storage,and sensible heat flux are found to be minor.

Calculation of Measurement Uncertainty for Stiffness Modulus of Asphalt Mixture

Asphalt mixture is a highly heterogeneous material, which is one of the reasons for high measurements uncertainty when subjected to tests. The results of such tests are often unreliable, which may lead to making bad professional judgments. They can be avoided by carrying out reliable analyses of measurement uncertainty adequate for the research methods used and conducted before the actual research is done. This paper presents the calculation of measurements uncertainty using as an example--the determination of the stiffness modulus of the asphalt mixture, which, in turn, was accomplished using the indirect tension method. The paper also shows the employment of the basic methods of statistical analysis, such as testing two mean values and conformity tests. Essential concepts in measurements uncertainty have been compiled and the determination of the stiffness module parameters are discussed. It has been demonstrated that the biggest source of error in the stiffness modulus measuring process is the displacement measure. The aim of the research was to find the measurement uncertainty for stiffness modulus by an indirect tensile test and the presentation of examples of the used statistical methods.

Projection of global mean surface air temperature changes in next 40 years: Uncertainties of climate models and an alternative approach

The Fourth Assessment Report (AR4) of the Intergovernmental Panel of Climate Change (IPCC) concluded that the climate projection using climate models that took account of both human and natural factors provided credible quantitative estimates of future climate change; however, the mismatches between the IPCC AR4 model ensembles and the observations, especially the multi-decadal variability (MDV), have cast shadows on the confidence of the model-based decadal projections of future cli mate. This paper reports an evaluation of many individual runs of AR4 models in the simulation of past global mean tempera ture. We find that most of the individual model runs fail to reproduce the MDV of past climate, which may have led to the overestimation of the projection of global warming for the next 40 years or so. Based on such an evaluation, we propose an al ternative approach, in which the MDV signal is taken into account, to project the global mean temperature for the next 40 years and obtain that the global warming during 2011–2050 could be much smaller than the AR4 projection.

Impacts and uncertainty analysis of elevated temperature and CO_2 concentration on wheat biomass

Impacts of climatic change on agriculture and adaptation are of key concern of scientific research. However, vast uncertainties exist among global climates model output, emission scenarios, scale transformation and crop model parameterization. In order to reduce these uncertainties, we integrate output results of four IPCC emission scenarios of A1 FI, A2, B1 and B2, and five global climatic patterns of HadCM3, PCM, CGCM2, CSIRO2 and ECHAM4 in this study. Based on 20 databases of future climatic change scenarios from the Climatic Research Unit （CRU） , the scenario data of the climatic daily median values are generated on research sites with the global mean temperature increase of 1℃（GMT＋ID）, 2℃（GMT＋2D） and 3℃（GMT＋3D）. The impact of CO2 fertilization effect on wheat biomass for GMT＋I D, GMT＋2D and GMT＋3D in China＇s wheat-producing areas is studied in the process model, CERES-Wheat and probabilistic forecasting method. The research results show the CO2 fertilization effect can compensate reduction of wheat biomass with warming temperature in a strong compensating effect. Under the CO2 fertilization effect, the rain-fed and irrigated wheat biomasses increase respectively, and the increment of biomass goes up with temperature rising. The rain-fed wheat biomass increase is greater than the irrigated wheat biomass. Without consideration of CO2 fertilization effect, both irrigated and rain-fed wheat biomasses reduce, and there is a higher probability for the irrigated wheat biomass than that of the rain-fed wheat biomass.