The error source analysis of oil spill transport modeling: a case study

Numerical modeling is an important tool to study and predict the transport of oil spills. However, the accu- racy of numerical models is not always good enough to provide reliable information for oil spill transport. It is necessary to analyze and identify major error sources for the models. A case study was conducted to analyze error sources of a three-dimensional oil spill model that was used operationally for oil spill forecast- ing in the National Marine Environmental Forecasting Center （NMEFC）, the State Oceanic Administration, China. On June 4, 2011, oil from sea bed spilled into seawater in Penglai 19-3 region, the largest offshore oil field of China, and polluted an area of thousands of square kilometers in the Bohai Sea. Satellite remote sensing images were collected to locate oil slicks. By performing a series of model sensitivity experiments with different wind and current forcings and comparing the model results with the satellite images, it was identified that the major errors of the long-term simulation for oil spill transport were from the wind fields, and the wind-induced surface currents. An inverse model was developed to estimate the temporal variabil- ity of emission intensity at the oil spill source, which revealed the importance of the accuracy in oil spill source emission time function.

Decoy-state reference-frame-independent quantum key distribution with both source errors and statistical fluctuations

Reference-frame-independent quantum key distribution （RFI QKD） can generate secret keys without the alignment of reference frames, which is very robust in real-life implementations of QKD systems. However, the performance of decoy-state RFI QKD with both source errors and statistical fluctuations is still missing until now. In this paper, we investigate the performance of decoy-state RFI QKD in practical scenarios with two kinds of light sources, the heralded single photon source （HSPS） and the weak coherent source （WCS）, and also give clear comparison results of decoy-state RFI QKD with WCS and HSPS. Simulation results show that the secret key rates of decoy-state RFI QKD with WCS are higher than those with HSPS in short distance range, but the secret key rates of RFI QKD with HSPS outperform those with WCS in long distance range.

STRONG CODING THEOREM AND ASYMPTOTIC ERROR EXPONENT OF ARBITRARILY VARYING SOURCE

Csiszar's strong coding theorem for discrete memoryless scarce is generalized to arbitrarily varying source.We also determine the asymptotic error exponent for arbitrarily wrying source.

Evaluation of the Arctic Sea-Ice Simulation on SODA3 Datasets

This study evaluates the Arctic sea-ice simulation of the SODA3 dataset driven by different atmospheric forcing fields and explores the errors of the Arctic sea-ice simulation caused by the forcing field.We find that the SODA3 data driven by different forcing fields represent a significant systematical error in the simulation of Arctic sea-ice concentration,showing a low concentration of thick ice and a high concentration of thin ice.In terms of sea-ice extent,the SODA3 data from different versions well characterize the interannual variability and declining trend in the observed data,but they overestimate the overall Arctic sea-ice extent,which is related to excessive simulation of ice in the sea-ice margin.Compared to observations,all the chosen SODA3 reanalysis versions driven by different atmospheric forcing generally tend to underestimate the Arctic sea-ice thickness,especially for thick ice in the multi-year sea-ice regions.Inaccurate simulations of Arctic sea-ice transport may partly explain the error in SODA3 sea-ice thickness in multi-year sea-ice areas.The results of different SDOA3 versions differ greatly in the Beaufort Sea,the Fram Strait,and the Central Arctic Sea.The difference in sea-ice thickness among different SODA3 versions is primarily due to the thermodynamic contribution,which may come from the diversity of atmospheric forcing fields.Our work provides a reference for using SODA3 data to study Arctic sea ice.

Modified wavelet filtering algorithm applied to gyro servo technology for the improvement of test-precision

In order to improve the measurement-precision of the gyro,the gyro experiment is completed based on gyro servo technology.The error sources of gyro servo technology are analyzed in the process of measurement,and the impact of these error sources on measurement is evaluated.To eliminate interference signal existing in the sampled data of the measurement,a modified wavelet threshold filtering method is presented.The results of the simulation and measurement show that the estimation-precision of the proposed method is improvement remarkably compared with the fast Fourier transform method,and the calculation work is reduced compared with the conventional wavelet threshold filtering methods,furthermore,the phenomenon of a common threshold of ＂killing＂ is solved thoroughly.

Tank Fire Control Systems Accuracy Assignment Based on Fuzzy Comprehensive Judgment Method

A method of accuracy assignment based on fuzzy comprehensive judgment method (FCJM) in tank fire control system is proposed. From the flowing route of the error sources and their respective correlative signals, the transfer functions of several sources are analysed by means of mathematic simulation, and FCJM is applied to obtain the cost comprehensive factor for each part of system, combining its error sensitivity factor the mathematical model is built to solve the accuracy assignment problem. Simulation result shows the proposed method can help designer of tank fire control system work out an optimal system more efficiently and more economically.

Research on Influence Mechanism of Transmission Accuracy for Harmonic Drive Mechanism Considering Multi-factor Coupling

The influence mechanism of transmission accuracy for harmonic drive mechanism considering multi-factor coupling was studied. According to analysis of influence factors of transmission accuracy for harmonic drive mechanism, it was obtained that the transmission errors of harmonic drive mechanism include processing errors and installation errors. The transmission error is produced by eccentric vector, it directly affects the rotation angle of output shaft and it makes harmonic drive mechanism produce backlash. Then analyze the movement error caused by the rigid wheel machining error, the flexible wheel machining error, the assembly error of the rigid wheel and the flexible wheel, the wave generator component, and the comprehensive expression method of motion error generated by each error source was obtained. The performance test device of space drive mechanism was used to test, and the law of the transmission accuracy of harmonic drive mechanism with temperature, speed and assembly clearance was obtained. The test results show that the transmission accuracy of harmonic drive mechanism decreases with increasing temperature, and the speed has little effect on the transmission accuracy of harmonic drive mechanism;the assembly quality has a significant impact on harmonic drive accuracy.

Evaluation of Arctic Sea-ice Cover and Thickness Simulated by MITgcm

A regional Arctic Ocean configuration of the Massachusetts Institute of Technology General Circulation Model(MITgcm)is applied to simulate the Arctic sea ice from 1991 to 2012.The simulations are evaluated by comparing them with observations from different sources.The results show that MITgcm can reproduce the interannual and seasonal variability of the sea-ice extent,but underestimates the trend in sea-ice extent,especially in September.The ice concentration and thickness distributions are comparable to those from the observations,with most deviations within the observational uncertainties and less than 0.5 m,respectively.The simulated sea-ice extents are better correlated with observations in September,with a correlation coefficient of 0.95,than in March,with a correlation coefficient of 0.83.However,the distributions of sea-ice concentration are better simulated in March,with higher pattern correlation coefficients(0.98)than in September.When the model underestimates the atmospheric influence on the sea-ice evolution in March,deviations in the sea-ice concentration arise at the ice edges and are higher than those in September.In contrast,when the model underestimates the oceanic boundaries’influence on the September sea-ice evolution,disagreements in the distribution of the sea-ice concentration and its trend are found over most marginal seas in the Arctic Ocean.The uncertainties of the model,whereby it fails to incorporate the atmospheric information in March and oceanic information in September,contribute to varying model errors with the seasons.

Discussion of sources of error in laser-speckle based systems

Applying laser-speckle techniques in material sciences as well as in methods to characterize surface con- ditions of specimen has become the method of choice, especially if a non-contacting principle is sought. This is almost always the case for specimen that are small in at least one dimension as for example in the materiM testing of foils, fibres, or micromaterials and certainly also if elevated test-temperatures are preventing standard gauges. This letter discusses in some detail sources of error that are quite often over- looked or not even considered as significant at all, but still carry the potential to introduce uncertainties well above the system design specifications.

Evaluation of sulfur trioxide detection with online isopropanol absorption method

Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas, and its concentration is generally two orders of magnitude lower than the SO2 concentration. The SO3 concentration can be measured online by the isopropanol absorption method; however, the reliability of the test results is relatively low. This work aims to find the error sources and to evaluate the extent of influence of each factor on the measurement results. The test results from a SO3 analyzer showed that the measuring errors are mainly caused by the gas–liquid flow ratio, SO2 oxidation, and the side reactions of SO3. The error in the gas sampling rate is generally less than 13%. The isopropanol solution flow rate decreases 3% to 30% due to the volatilization of isopropanol, and accordingly, this will increase the apparent SO3 concentration. The amount of SO2 oxidation is linearly related to the SO2 concentration. The side reactions of SO3 reduce the selectivity of SO42- to nearly 73%. As sampling temperature increases from180 to 300°C, the selectivity of SO42- decreases from 73% to 50%. The presence of H2 O in the sample gas helps to reduce the measurement error by inhibiting the volatilization of the isopropanol and weakening side reactions. A formula was established to modify the displayed value, and the measurement error was reduced from 25%–54% to less than 15%.

INFLUENCE OF INTERACTION BETWEEN LOW AND MIDDLE LATITUDES ON ENSO VARIABILITY IN THE CANE-ZEBIAK MODEL

In this paper,an error source in the atmospheric component of the CZ(Cane-Zebiak)model is discussed,which is missing a free mode in“the exact solutions”.However,the improved scheme is proposed,which is the computational scheme with adjusted wind or observed u and v as lateral boundaries.The simulations show that the simulated surface wind by the improved scheme strong- ly bears resemblance to the observation except for the area near the west and the east boundaries of the integrated area.These results support the conclusion that the wind stress simulated by the im- proved scheme with lateral boundaries is much better than that simulated by the CZ model,and show that interaction between low and middle latitudes has an important influence on the ENSO variability in the CZ model.Therefore,considering its impact on the CZ model can improve capa- bility of the CZ model for simulating ENSO variability.

Compact trimming design of a high-precision reference

To design a high-precision reference, the various error sources have been analyzed and compensated with a compact 111 mV resistor-trim scheme and the upper and lower extremes of the reference precision are also temperature-compensated. At room temperature, the yield of ：50.5% precision is 96% and ：50.2% is 78%.