Warning Lines Research Articles

How large is the collapsed area of ground collapse induced by tunnelling

ABSTRACT Ground collapse has frequently been reported in recent years, which poses a great threat to the safety of human beings and property. This study aims to determine the collapsing diameter and volume of tunnelling-induced ground collapse by analytical method. Firstly, assuming that the surface of collapsed block is sliding along a planar surface, and the sliding area is derived based on the limit equilibrium method. Then, the collapse volume is derived by combining with the equation of the collapse trajectory. Lastly, the proposed method is verified by a physical modelling test. The results show that (i) as the unit weight of soil, buried-depth and the radius of tunnel increase, the influencing diameter and collapse volume gradually increase; (ii) with the increase in the cohesion and friction angle of the soil, the influencing diameter and collapse volume gradually decrease. Dongquan Tunnel is taken as a case study, the influencing diameter of ground by using the proposed approach is compared with the one in practical engineering. This study provides a theoretical guideline to mark the collapse warning lines by the potential ground collapse area, which is induced by excavation of shallow-buried tunnels or underground structures.

Shadow Education in China and Its Diversified Normative Governance Mechanism: Double Reduction Policy and Internet Public Opinion

As a private supplementary education activity outside the formal education system, shadow education aims to help students pass exams smoothly and obtain better educational resources. In 2021, The Chinese Government issued “Opinions on Further Reducing the Burden of Students’ Homework and Off-campus Training in Compulsory Education” (referred to as the “double reduction” policy for short). We aim to strengthen the standardization of out-of-school training institutions and stimulate public debate on the Internet. However, research on the double reduction policy and how to guide the reform of shadow education in combination with online public opinion is still lacking. Based on this, the text of the double reduction policy and the popular spots for the development of online public opinion were selected for a text analysis, and a diversified and standardized governance mechanism of China’s shadow education was constructed. The results of this study show that the shadow education reforms need to pay attention to government policy documents and network public opinion, and develop public opinion warning lines. This study can provide the international academic community with information on China’s shadow education reform, providing valuable experience and a reference.

Estimating stock pledge rate using VaR and modified ES model

ABSTRACT This study mainly focuses on the reasonable determination of the stock pledge rate in the A-share market. Based on the Value-at-Risk (VaR) and modified Expected Shortfall (ES) models, 137 sample stocks were used to measure the pledge rate of stocks. The breakdown times and breakdown probability were used to verify the validity of the two models. Firstly, the results indicate that the adjusted breakdown probability calculated by the two models is less than 5%, the two models are highly reliable in measuring the stock pledge rate. Secondly, the stock pledge rate measured by the modified ES model is more effective compared with the VaR model. Finally, the prediction results of modified ES are still robust under different warning lines and liquidation lines.

Event-based rainfall warning regression model for landslide and debris flow issuing

Debris flow and landslide warnings are currently based on real-time monitoring of rainfall according to predefined warning lines. Conventionally, the rainfall variables combinations cumulative rainfall–duration (Re–D) and mean rainfall intensity–cumulative rainfall (Im–Re) for setting rainfall thresholds are used separately for landslide warning. The variables used in the regression analysis are correlated and a physical relationship Im = Re/D is available. Two-dimensional warning lines lack spatial feature and may not sufficiently reflect the rainfall characteristics required to initiate debris flows. A technical procedure using 3D regression analysis of the rainfall parameters interaction analysis was proposed. The rainfall warning regression surface is set on the basis of rainfall variables such as average rainfall intensity, effective cumulative rainfall, and duration. Here, a three-parameter, paraboloid rainfall warning regression surface generated using the variables of Im, D, and Re to determine the rainfall characteristics necessary to initiate debris flows and landslides is proposed. The proposed rainfall warning regression model reflects the rainfall characterization using a 3D diagram than the conventional threshold line. The regression results are converted in a multiple Im–D rainfall warning regression diagram containing various Re quantities for issuing landslide and debris flow warnings. Results show that the types of rainfall required to initiate debris flows and landslides include high rainfall intensity within a short duration and high cumulative rainfall over a long duration; moreover, debris flows could be affected by postseismic effects. The regression surfaces vary for rainfall events associated with different typhoons, which suggest that the initiation of landslides and debris flows is affected by the event that causes rainfall. An inclined plane surface is commonly used for describing a rainfall-induced landslide and debris flow regression surface for issuing warnings. The regression surface has parabolic geometry in postseismic landslide areas. The interactions of rainfall parameters using a three-dimensional regression analysis were studied and it was applied to the case of a catastrophic landslide and debris flow at Xiaolin Village in Taiwan.

Joint optimisation of double warning T2-Hotelling chart and maintenance policy with multiple assignable causes

ABSTRACTStatistical process monitoring (SPM) and maintenance management as two key tools for process management can create profound economic benefits, particularly when they are coordinated. This paper demonstrates the value of integrating SPM and maintenance by presenting a multi-objective model consisting of both economic and statistical criteria. Furthermore, to more adapt to complex manufacturing systems, the proposed model consists of two features: (1) monitoring several correlated quality characteristics by designing a double warning lines ‘T2-Hotelling’ chart; and (2) considering the probability of occurrence for more than one assignable cause (AC). To show the effectiveness of the proposed integrated model, two comparative studies are conducted. The first one confirms that the integration of SPM and maintenance policy leads to more effective performance in both economic and statistical viewpoints. The latter results demonstrate that the proposed model outperforms the corresponding single objective models.

An integration of NSGA-II and DEA for economic–statistical design of T2-Hotelling control chart with double warning lines

Control charts are the most applicable tools for monitoring the quality of processes. The day-to-day changes in industrial processes and customers’ expectations motivate the process engineers to monitor multiple correlated quality characteristics, simultaneously. Hence, in this paper, the design of a “double warning lines T2-Hotelling” control chart is studied because of the advantages of this multivariate control chart in detecting moderate and small shifts in a process. In this regard, this research aims to optimize a multi-objective economic–statistical design model that considers monitoring costs and statistical features of control chart, concurrently. The non-dominated sorting genetic algorithm II is utilized to obtain a suitable Pareto set for the model. Since it is difficult for the decision makers to select the most efficient solution among the Pareto set, three different methods of data envelopment analysis consisting of Charnes–Cooper–Rhodes model, cross-efficiency technique and aggressive formulation are used to rank the members of Pareto set and to select the most efficient one. Also, in this research the performance of these three methods in discriminating between the efficient solutions is compared to each other. Eventually, a comparative study is conducted to show the better performance of the suggested model in comparison with the corresponding economic design model.

Procedural Warning System Study on Irrigation Reservoirs

Warning lines of surface water, which are important parts of the red line of water resources control and development, have theoretical significance and practical value to comprehensive utilization and scientific management of water resources. Based on the use control line of three red lines, this paper proposed the conception of procedural warning firstly, and gave warning management method of irrigation reservoirs. In the case of the Douyazi Reservoir in Jiaonan, procedural warning lines were given with warning period of non-flood, warning management which supported utilizing water resources reasonably and efficiently with technical basis.

Variable Sampling Rate Multivariate Exponentially Weighted Moving Average Control Chart with Double Warning Lines

This study investigates the variable sample sizes and variable sampling intervals multivariate exponentially weighted moving average control chart using double warning lines (MEWMA-DWL). The steady-state average time to signal of the MEWMA-DWL control chart is obtained by using the Markov chain approach. Then the performance of the MEWMA-DWL control chart is compared with the corresponding fixed sampling rate (FSR) MEWMA control chart. From the numerical results, the MEWMA-DWL control chart is faster than the corresponding FSR MEWMA control chart in detecting small and moderate shifts in the process mean vector.

On the advantages of economically designed variable sample sizes and sampling intervals T2 control chart: double warning lines scheme

Faraz and Parsian (Stat Pap 47:569–593, 2006) have shown that the double warning lines (DWL) scheme detects process shifts more quickly than the other variable ratio sampling schemes such as variable sample sizes (VSS), variable sampling intervals (VSI) and variable sample sizes and sampling intervals (VSSVSI). In this paper, the DWL T2 control chart for monitoring the process mean vector is economically designed. The cost model proposed by Costa and Rahim (J Appl Stat 28:875–885, 2001) is used here and is minimized through a genetic algorithm (GA) approach. Then the effects of the model parameters on the chart parameters and resulting operating loss is studied and finally a comparison between all possible variable ratio sampling (VRS) schemes are made to choose the best option economically.

Multi-component out-of-specification test results: a case study of concentration of pesticide residues in tomatoes

A metrological approach is used for investigating multi-component out-of-specification (OOS) test results of pesticide residues concentration in tomatoes. As a case study, 169 test results were obtained in Israel in 2009. Five of the test results were OOS test results exceeding the national legal maximum residue limits (MRL). Only one of them was classified definitely (with more than 0.99 confidence) as caused by a farmer’s/producer’s problem. The other four OOS test results were probably metrologically related, i.e., compatible with MRL when considering the measurement uncertainty associated with the test results. A new parameter—the ratio of a test result to MRL—was proposed for analysis of tomatoes monitoring multi-residue data as a common statistical sample from the same population for different pesticide residues. Weibull distribution was found adequate for modeling the empirical distribution of the parameter values. Probability of future OOS test results was estimated, and global risks of farmer/producer and consumer/buyer were evaluated. Acceptance limits for the test results, such as “warning and action lines” in quality control charts, were calculated by taking into account the measurement uncertainties.

Investigating out-of-specification test results of mass concentration of total suspended particulates in air based on metrological concepts—a case study

A metrological approach is used for investigating out-of-specification (OOS) test results of total suspended particulate matter (TSP) mass concentrations in ambient air. As a case study, 496 test results of mass concentration of TSP in ambient air were obtained according to methods of the Environmental Protection Agency, USA. The samples, collected in 2009, came from the same geographic proximity in three stone quarries located in Israel. Twenty of the test results were OOS test results that exceeded the upper limit specified in the national air quality regulations. Investigation of the OOS test results indicated the fact that only 10% of these results (two out of 20) can be decidedly interpreted as witnesses of violations of the national air quality regulations. The other 90% were probably metrologically related, i.e., compatible with the national air quality regulations when considering the measurement uncertainty associated with the test results. Probabilities of future OOS test results and global risks of the stone producer and the consumer, who is defined as an inhabitant near a quarry, were estimated. Acceptance limits, resembling “warning and action lines” used in quality control charts, for air test results were calculated by taking into account the measurement uncertainty.

On the advantages of economically designed the Hotelling’s T2 control chart with variable sample sizes and sampling intervals

Faraz and Parsian (Statistical Paper, 47: 569–593, 2006) have shown that the double warning lines (DWL) scheme detects process shifts more quickly than the other variable ratio sampling schemes such as variable sample sizes (VSS), variable sampling intervals (VSI) and variable sample sizes and sampling intervals (VSSVSI). In this paper, the DWLT2control chart for monitoring the process mean vector is economically designed. The cost model proposed by Costa and Rahim (Journal of Applied Statistics, 28: 875–885, 2001) is used here and is minimized through a genetic algorithm (GA) approach. Then the effects of the model parameters on the chart parameters and resulting operating loss is studied and finally a comparison between all possible variable ratio sampling (VRS) schemes are made to choose the best option economically.

Credit risk measurement and early warning of SMEs: An empirical study of listed SMEs in China

In the process of resolving financing difficulties of small and medium enterprises (SMEs) in China, the measurement of credit risk of SMEs is a very challenging problem. In this paper we develop a novel model based on the original KMV model with tunable parameters to measure the credit risk of Chinese listed SMEs. By setting two credit warning lines to monitor the credit crisis of listed SMEs, we find that the predictive accuracy of adjusted KMV model is stable to the change of default points in Chinese listed SMEs, which is different from KMV Company's existing result. Our study shows that the credit risk of listed SMEs in China is relatively high and tends to increase during the chosen period from the year 2004 to 2006. We also find that the asset size has significant impact on credit risk and there are few credit risk fluctuations before and after the split share structure reform.

Hotelling’s T2 control chart with double warning lines

Recent studies have shown that the T2 control chart with variable sampling intervals (VSI) and/or variable sample sizes (VSS) detects process shifts faster than the traditional T2 chart. This article extends these studies for processes that are monitored with VSI and VSS using double warning lines (T2—DWL). It is assumed that the length of time the process remains in control has exponential distribution. The properties of T2—DWL chart are obtained using Markov chains. The results show that the T2—DWL chart is quicker than VSI and/or VSS charts in detecting almost all shifts in the process mean.

A New Look at Warning and Action Lines of Surveillance Schemes

A New Look at Warning and Action Lines of Surveillance Schemes

A New Look at Warning and Action Lines of Surveillance Schemes

Abstract Some authors have suggested an efficient dynamic monitoring procedure for detection of a change in the drift of a Brownian motion. Their procedure can be described as a sequence of extremely short sequential probability ratio tests (SPRT's) done in zero time with infinitesimal time between consecutive SPRT's. The drawbacks of this procedure are that it can be described only as a limit of practical procedures and it does not take into account the cost of initiating a test. In this article, we suggest a procedure that takes both sampling and overhead costs into account and that can reasonably be carried out in practice. In this procedure the process is monitored continuously with a constant sampling rate. The accumulated data are analyzed by the standard cumulative sum (CUSUM) statistics. Whenever the CUSUM procedure raises an alarm, data are accumulated as fast as possible until either the alarm is relaxed or the process is stopped.

Controlling the Standard Deviation by Cusums and Warning Lines

The usual process inspection scheme for controlling the standard deviation (S.D.) of a normal distribution is to plot a Shewhart chart on which are recorded the ranges of small samples; a common size is 5 items. Action is taken if any sample range exceeds a previously determined amount. The rapidity with which the scheme detects a departure from the accepted value of σ can be increased by considering the results of several of the latest samples together. A fixed number of samples can be taken into account by Warning Lines on the Shewhart-type chart (4); a more sensitive scheme uses cumulative sums (cusums) of the sample ranges together with a rule for deciding what change of direction of the cusum path should require action. Both these approaches can be applied to gauged observations. In this paper we compare these four schemes and provide a short table of cusum schemes using the range.

Controlling the Standard Deviation by Cusums and Warning Lines

Controlling the Standard Deviation by Cusums and Warning Lines