Coefficient Correction Method Research Articles

Probability and Severity Based Overvoltage Risk Analysis Considering Large-Scale DG Access

Abstract With the rapid increase of distributed generation (DG) in the distribution network (DN), the analysis of DG maximum bearing capacity (DGMBC) is paid more attention. However, the existing methods can not precisely simulate the overvoltage risk concerning occurrence probability and severity. To this end, the overvoltage scenario classification method and overvoltage severity coefficient correction method are proposed in this paper, which can effectively reflect the real overvoltage risk in DN. The IEEE 33-bus test feeder is used to compare the calculation results of overvoltage risk with other methods.

Spatial and Temporal Evolution and Impact Factors Analysis of Ecosystem Service Value in the Liaohe River Delta over the Past 30 Years

An in-depth study of the spatiotemporal variation characteristics and driving factors of ecosystem service values in the Liaohe River Delta is of great significance to its ecological environment governance and protection. Based on the land use data of the Liaohe River Delta for seven periods from 1990 to 2020, the ecosystem service value (ESV) was evaluated according to the equivalent factor coefficient correction method, establishing models for estimating the value of ecosystem services; the spatial and temporal evolution characteristics of the ESV in the study area were comprehensively analyzed; and the driving influencing factors and mechanisms of the ESV were explored. The results showed that:① From 1990 to 2020, the most common land use type in the Liaohe River Delta was cultivated land, and the areas of forest land, wetland, and unutilized land showed a decreasing trend; grassland, water, and construction land showed an increasing trend; and the area of cultivated land was basically unchanged during the 30 year period. ② In terms of the temporal evolution, the ESV in the study area showed a trend of first decreasing, then increasing, and then decreasing. In terms of the spatial distribution of ESV, the total value of ecosystem services as a whole showed a spatial divergence pattern of a high value in the southwest and low value in the northeast. ③ The sensitivity index of all land use types in the Liaohe River Delta was less than 1, indicating that the ESV was inelastic. ④ The value of ecosystem services in the Liaohe River Delta showed positive spatial coherence. On the whole, the Liaohe River Delta was dominated by HH and LL clusters, with HL clusters mostly distributed at the boundaries of LL clusters and LH clusters distributed at the boundaries of HH clusters. ⑤ Among the factors influencing the evolution of ESV in the Liaohe River Delta, DEM had the least influence, and HAI had the greatest influence on the ESV, followed by precipitation. The interaction results of all influencing factors had an enhancing effect on the spatial distribution of the ESV, among which HAI and precipitation had the strongest interaction effect, reaching 95.58%.

A 3D thermal conductivity prediction method for deep strata based on temperature field estimation

Accurate predictions of earth’s interior thermal conductivity are essential for interpreting the mechanisms involved in geothermal systems and delineating geothermal resource targets. Existing thermal conductivity prediction methods, which typically involve measurements of rock samples and predictions based on geophysical well logging, cannot accurately predict regional thermal conductivity distributions. We develop a 3D thermal conductivity prediction based on temperature field estimation. First, the finite-element method is used for temperature forward modeling. Subsequently, the inexact Gauss-Newton method is implemented in the prediction algorithm. Synthetic studies indicate that the method can recover the true model well. The subsurface temperature distribution of the Xiong’an New Area is predicted using the coefficient correction method of the optimal temperature. Next, we obtain the 3D distribution of thermal conductivity of deep formation in the Xiong’an New Area with the predicted temperature field. The distribution of terrestrial heat flow also is estimated. In addition, the law of thermal accumulation of strata at different depths is analyzed, and the internal relation among resistivity, temperature, and thermal conductivity is studied. Thus, the 3D thermal conductivity prediction method provides the theoretical basis for interpreting mechanisms for the origin of geothermal systems and heat accumulation patterns. It could have significant utility for the analysis of geothermal fields and the sustainable development and use of geothermal resources.

Thermal airflow sensor design and temperature compensation research based on the thermostatic method

PurposeThis paper aims to solve the typical thermal airflow sensor's high power consumption and integration difficulties, based on the FS5 thermal element and constant temperature measurement method, a flow sensor is developed with high measurement accuracy, low power consumption, small size, low cost and easy system integration.Design/methodology/approachA small wind tunnel was used to test and assess the sensor's measurement range, reaction time, stability, repeatability, measurement accuracy and multi-temperature calibration was performed in the temperature range of −10°C to 30°C. The effect of ambient temperature on the sensor's measurement data is investigated, and the coefficient correction method of power function was investigated to implement the sensor's software temperature compensation function.FindingsThe results show that the sensor is stable and repeatable, the output voltage has a power function relationship with the airflow rate, the flow rate measurement range is 0–18 m/s, the response time is less than 3 s, the measurement accuracy at high flow rates is within 0.4 m/s and the temperature-corrected airflow rate measurement error is less than 5%. Setting the temperature calibration interval to 2°C and 5°C has the same temperature compensation effect, reducing the sensor's calibration effort significantly.Originality/valueThis paper demonstrates that a thermostatic method is used to construct a thermal wind speed sensor that delivers accurate measurements in the wind speed measuring range of 0–18 m/s under test conditions. In addition, the sensor's performance is evaluated, and calibration tests for a wide range of temperatures are done. Finally, based on the power function correction method, a temperature compensation algorithm is proposed.

Subsurface temperature prediction by means of the coefficient correction method of the optimal temperature: A case study in the Xiong’an New Area, China

Accurate estimation of the earth’s interior temperature is extremely important for studying fundamental scientific and applied geothermal problems. Existing temperature estimation methods cannot provide reliable accuracy in the cross-borehole space and beyond the borehole’s depth; however, resistivity could overcome this difficulty as a temperature-dependent proxy parameter. At present, this approach is based on the use of purely empirical formulas, whose validity is unjustifiably postulated to be invariant with respect to geologic settings. We develop an electromagnetic (EM) geothermometer based on the coefficient correction method of the optimal temperature (CCMOT). This geothermometer can accurately determine the relationship between the normalized resistivity and temperature in an underground space based on resistivity-temperature logging data and EM data; therefore, a visualized temperature distribution can be calculated. The CCMOT is applied to the subsurface temperature prediction in the Xiong’an New Area, with an accuracy of 86.69%–97.25%. Sensitivity analysis of the key variables of the CCMOT reveal that the CCMOT has relatively little dependence on the number of constraining boreholes and the optimization of the subdivision spacing of the logging data can significantly improve temperature prediction accuracy. The CCMOT can be used to determine the distribution of the heat structure of the reservoir and to interpret the geothermal field. In addition, the CCMOT is of great significance to the evaluation, scientific development, and sustainable use of geothermal resources.

Droop coefficient correction control for power sharing and voltage restoration in hierarchical controlled DC microgrids

With the widely application of the DC microgrid (MG), the utilization of renewable resources is improved by interconnecting nearby DC MGs. Since MGs are connected by different line impedances, the intuitive tradeoff exists between the conflicting goals of current sharing and voltage regulation in the conventional droop control scheme. A hierarchical control structure with a dynamic droop coefficient correction control (DCCC) is presented to achieve better power sharing in DC MGs. In the proposed hierarchical control scheme, the droop coefficient correction method is employed in the primary level, which corrects the droop coefficient automatically and the proportional current has been shared. Moreover, the droop coefficient of each converter is also dynamically adjusted to deal with the impact of uncertain line impedances. The robustness of performance to system uncertainties is also demonstrated. Meanwhile, the different current ratio of the microgrids can be provided to the DC bus by using the tertiary control level, which achieves an arbitrary power sharing among the microgrids. In addition, a small-signal model is developed to investigate the effects of coupling relationship in the control parameters in the voltage loop, voltage restoration controller and droop coefficients. Finally, the experimental results are presented to evaluate the effectiveness of droop coefficient correction control approach and hierarchical control scheme for the DC MG under resistive and constant power load (CPL) conditions.

Improvement of plutonium sample property measurement based on fast neutron multiplicity counting

Fast neutron multiplicity counting have (FNMC) is a new method of non-destructive analysis for nuclear materials. The new measurement equations of the fourth-order FNMC was established for plutonium samples. Based on the analysis of equations, a set of FNMC with three layers and six liquid scintillations in each layer is set up considering crosstalk, and the single crosstalk rate κ is determined to be 5.68‰. In addition, the quality of Pu and the measurement deviation correction under the different shell materials conditions were analyzed respectively. Finally, the third-order polynomial fitting equations under the condition of multiplication coefficient and (α, n) reaction rate are obtained by modifying the solution quality of Pu. Within the mass range of 500 g Pu, the corrected deviation was less than ±6%. The results show that the combination of FNMC and the coefficient correction method can achieve a more accurate measurement of Pu properties.

Low Velocity Impact Energy Monitoring and Recognition of Composite Laminates with Variable Thickness Based on Optical Fiber Sensor Network

At present, most of the research on low velocity impact of composite laminates focuses on load location and damage assessment. To provide further early warnings about structural impact damage, impact energy can be monitored and identified. For high strength composite laminates with variable thickness, in order to further accurately evaluate the impact energy, it is necessary to adopt more suitable dynamic load signal analysis and impact energy identification methods. Therefore, a new low velocity impact monitoring and identification method for composite plates with variable thickness is proposed. All impact sample signals collected by optical fiber sensor network are decomposed by whitening Empirical Mode Decomposition (EMD); the energy feature set is established according to the impact energy eigenvalue of sample signal; according to the first order component of signal decomposition, the thickness coefficient is determined and the energy feature set is modified to evaluate the actual impact energy. Meanwhile, combined with optical fiber sensing and signal processing technology, an impact energy monitoring system has been established, and the low velocity impact monitoring and identification experiments of composite laminates with variable thickness were carried out. The proposed energy identification method successfully identified 1–3 J impact energy with an average error of 4.82%, and the average error of large thickness area with low sensitivity was significantly reduced from 13.25% to 5.67%. The results show that the thickness coefficient correction method based on whitening EMD can evaluate the low velocity impact energy more accurately, and the thickness coefficient correction step significantly improves the recognition performance.

Calculation of Nonlinear Stiffness of Rubber Pad under Different Temperatures and Prepressures

The static stiffness of rubber springs is affected by temperature and prepressure. In this thesis, the relationship between Young’s modulus and temperature of rubber was studied, and the quantitative relationship between them was determined. The approximate formula for calculating the static stiffness of rubber pads was further modified, and the ellipse approximation method and convexity coefficient correction method were proposed. In addition, the influence of temperature on geometric nonlinearity was considered. The formula for calculating nonlinear stiffness includes two variables: temperature and prepressure. The results of tests and theoretical calculations demonstrate that the nonlinear formula can be a good approximation and that it can meet the requirements of engineering applications.

Design and Experimental Verification of a 1/20 Scale Model of Quayside Container Crane Using Distortion Theory

The scale model is an effective method to research the performance of quayside container crane (QCC) under the seismic condition, but the model distortion usually exists in the similar design process which leads to the incomplete similarity between the scale model and prototype. In this investigation, the distortion theory and the prediction coefficient correction method are used to upgrade the quality of 1/20 QCC scale model and, then, the seismic response of the QCC prototype is obtained from the shake table scale model test. In the first step, the similarity ratio of the 1/20 QCC scale model is calculated by the similitude law and the size of scale model is obtained from the similarity constants. In the second step, the bending stiffness is selected and determined as the distortion term and, then, the relationship between the distortion coefficient and the prediction coefficient is obtained by the finite element prediction coefficient method. Furthermore, the three different scale models are manufactured and tested in the shake table experiment under different seismic conditions. It is found that the experimental test results are consistent with the numerical simulation results of the QCC prototype. It can be concluded that the QCC scale model can be used to predict the performance of the prototype under the different seismic conditions after corrected by distortion theory, and the distortion theory is an effective method to solve the incomplete similarity between the scale model and prototype.

Error analysis and correction of spatialization of crop yield in China – Different variables scales, partitioning schemes and error correction methods

Spatialization of crop yield is beneficial to comprehensive analysis between interdisciplinary data. Multivariable linear regression models are often applied to spatialization of attribute data. The variables scales and the partitioning of China should be considered when the model is constructed. Different variables scales and partitioning schemes will inevitably results in different spatialization errors. Spatialization errors can be reduced by error correction methods. Different methods have different influence on the accuracy of crop yield spatialization. In this study, three variables scales were selected including prefectural scale, county scale and grid cell (1 km × 1 km). Five partitioning schemes (no partition of China, 7 regions of China, 9 regions of China, 10 regions of China, partitions of China by province) were considered. A total of 28 kinds of multivariable linear regression models were constructed with area of different types of farmland as independent variables, crop yields as dependent variables. Then, seven kinds of error correction methods were used to correct crop yield spatialization results. Three error evaluation indicators were selected to investigate the influence of different variables scales, partitioning schemes and error correction methods on the precision of spatialization results. The conclusions can be drawn as follows: (a) Nine models with intercept based on variables at regional scale could not be used to spatialize crop yield, while the others can be used for spatialization of crop yield. (b) The precision of the spatialization result based on the model without intercept is higher than that based on the model with intercept. (c) For models without intercept, precision of spatialization results increased first and then decreased with the refinement of partitioning scheme. (d) For models without intercept, the precision of spatialization results improved with scaling down of the variables scale from prefectural scale to county scale and grid scale. (e) Among the seven kinds of error correction methods, average correction method, weight coefficient correction methodⅡ and weight coefficient correction method III can’t be used to correct initial spatialization results. (f) Proportional coefficient correction method, weight coefficient correction methodⅠ, weight coefficient correction method Ⅳ and weight coefficient correction method Ⅴ can be used to correct initial results of spatialization. (g) The precisions of corrected spatialization products based on error correction methods, which can improve the precision of initial spatialization products, are very closely. This research made up for the deficiency of spatial error analysis of crop yield, explored the relationship between different sample scales and partitioning schemes and spatial error, compared the pros and cons of different error correction methods. Meanwhile, it also provided valuable information for other types of social and economic statistical data.

A New Dynamic Model for Sealed Coring Saturation Correction in Hydrocarbon Reservoir

It is one of the most intuitive methods to analyze the formation of oil and water saturation by sealed coring. But this method is affected by a variety of factors, such as pore volume change, fluid compression, and separation of dissolved gas. In view of the impact of such factors on sealed coring test saturation, there are four kinds of correlation methods currently, namely, comprehensive coefficient correction method, experiment correlation method, mathematical statistics method, and mathematical model correction method, with their own advantages and disadvantages. Based on the analysis of physical change during core lifting process, this paper proposes the mathematical model for dynamic correction of core saturation based on dissolved gas drive filtration theory, multiphase flow fractional flow theory, and corresponding work flow. This method comprehensively considers the impact of relative permeability of three-phase fluid flow, elastic compression nature of fluid and rock, fluid viscosity, volume factor, solution GOR, and other high-pressure PVTs, so it features a wider adaptability, and the accuracy of model correction results satisfies the project requirements. This method provides a reliable basis for the true oil-water saturation of actual reservoir and has an important theoretical and practical significance.

基准价格系数修正法在海域一级市场价格评估中的应用研究

海域价格评估在海洋经济发展以及海域资源市场管理化过程中起着重要作用，它是保证海域有偿使用制度顺利实施的基础，也是国有资源性资产保值增值的保障。文章以台州市一宗工业用海为例详细阐述基准价格系数修正法在海域资源一级市场价格评估中的测算过程，并结合该方法的应用，探讨其适用性和局限性，提出克服局限性的建议。该研究对于我国开展海域资源一级市场使用权价格评估具有现实意义和借鉴作用。 The evaluation of sea area price plays an important role in the process of marine economic development and management of marine resources market. It is the basis for ensuring the smooth implementation of paid use system of the sea and the guarantee of the preservation and appreciation of state-owned assets. In this paper, the application of coefficient correction method of benchmark price in primary market of the sea area is analyzed to explore its applicability and limitations by taking a case of industrial sea in Taizhou for example, and puts forward the countermeasures to overcome the limitation. This study has important practical significance and reference for our country to carry out the price evaluation in primary market of the sea area.

Visibility Video Detection with Dark Channel Prior on Highway

Dark channel prior (DCP) has advantages in image enhancement and image haze removal and is explored to detect highway visibility according to the physical relationship between transmittance and extinction coefficient. However, there are three major error sources in calculating transmittance. The first is that sky regions do not satisfy the assumptions of DCP algorithm. So the optimization algorithms combined with region growing and coefficient correction method are proposed. When extracting atmospheric brightness, different values lead to the second error. Therefore, according to different visibility conditions, a multimode classification method is designed. Image blocky effect causes the third error. Then guided image filtering is introduced to obtain accurate transmittance of each pixel of image. Next, according to the definition meteorological optical visual range and the relationship between transmittance and extinction coefficient of Lambert-Beer’s Law, accurate visibility value can be calculated. A comparative experimental system including visibility detector and video camera was set up to verify the accuracy of these optimization algorithms. Finally, a large number of highway section videos were selected to test the validity of DCP method in different models. The results indicate that these detection visibility methods are feasible and reliable for the smooth operation of highways.

Error Analysis of Attenuation Coefficient of the Second Order Circuit

Circuit experiment is a very important professional basic course for students of electrical experiments. Experiment study is further validation of theoretical study and supplement. If the deviation between the experimental data and the theoretical value is large, it will not verify the theoretical value, instead it will make students feel puzzled. So if there is a problem, how to solve it? This paper is mainly from the experiment, numerical simulation and theoretical values to compare and determine the accuracy of measuring damping coefficient method under the condition of under-damped RLC second-order circuit. It also analyzes the reasons of the error, and then put forward the damping coefficient correction method.

Study on Turbulence Compensation Surveying and Mapping Algorithm of Ships

Research on ship photoelectric measuring instrument measurement error compensation technology, which can improve the accuracy of the measurement. According to the ship sailing in the influence of turbulence by the winds and waves, causing airlines direction deflection happen suddenly, and measurement data is not accurate with jumping up and down along the axis. In order to avoid these problems, this paper proposes a kind of ship turbulence measurement compensation algorithm, by adjusting the ship turbulence coefficient to predict the turbulence extend of the ship, and compensate the turbulence measurement error, use the ship turbulence coefficient correction method to revise the result of compensation, overcome turbulence effects impact. The experiment proves that the ship turbulence measurement compensation algorithm compensate measurement results, can improve the accuracy rate of measurement data and satisfactory results have been obtained.

A time-domain projection-based registration-scene-based nonuniformity correction technology and its detailed hardware realization

Non-uniformity (NU) in infrared images can cause great degradation of the image quality and appearance. Scene-based nonuniformity correction (SBNUC) has become a very effective way to deal with NU. Although many SBNUC methods have been developed by researchers worldwide, few of them have a good correction performance and can be applied to small-package real-time devices. In this paper, we propose a time-domain projection-based registrationscene-based NU correction technology and its detailed hardware realization. We developed a new projection estimator to calculate the relative displacement of neighboring frames. The estimator uses a column and row projection vector to calculate the displacement separately without reducing the accuracy. We also developed an improved gain coefficient correction method using the corrected bias coefficient to correct the gain coefficient by clarifying the intrinsic relationship between these two coefficients instead of correcting them separately. We have also thoroughly analyzed how this technology performs with an actual infrared video sequence containing both low-frequency and high-frequency NUs. The hardware realization of this technology in a single-FPGA-core real-time system is also described in detail. We have successfully realized this technology in a real engineering application. Detailed flow charts for the hardware implementation of this algorithm are also provided.

Characteristics of R-123 two-phase flow through micro-scale short tube orifice for design of a small cooling system

We present a new discharge coefficient correction method for the orifice equation for R-123 two-phase flows. In this method, an evaporator is mounted after the orifice as a vapor refrigeration cycle, and the evaporator is used to measure the quality of downstream flow through the orifice. Quality is estimated from the measured temperature and pressure of the evaporator inlet and outlet, respectively, instead of by direct measurement of quality. The condition of upstream flow of the orifice is the liquid state at 3 bar and 60 °C. The liquid flow is changed to two-phase flow after passing through the orifice. Orifice diameters of 300, 350, 400, and 450 μm are used for the experiment, and the results are analyzed. Experiments are conducted for various conditions of flow rate between 20 and 70 ml/min and for cooling loads of 60, 80, and 100 W. The results show that the quality of flow downstream from the orifice can be calculated using the enthalpy difference between the inlet and outlet of the evaporator. An equation to determine the discharge coefficient is formulated as a function of quality. We expect that these results can be used to help design a small cooling system.