Probabilistic analysis of tunnel face seismic stability in layered rock masses using Polynomial Chaos Kriging metamodel

Face stability is an essential issue in tunnel design and construction.Layered rock masses are typical and ubiquitous;uncertainties in rock properties always exist.In view of this,a comprehensive method,which combines the Upper bound Limit analysis of Tunnel face stability,the Polynomial Chaos Kriging,the Monte-Carlo Simulation and Analysis of Covariance method(ULT-PCK-MA),is proposed to investigate the seismic stability of tunnel faces.A two-dimensional analytical model of ULT is developed to evaluate the virtual support force based on the upper bound limit analysis.An efficient probabilistic analysis method PCK-MA based on the adaptive Polynomial Chaos Kriging metamodel is then implemented to investigate the parameter uncertainty effects.Ten input parameters,including geological strength indices,uniaxial compressive strengths and constants for three rock formations,and the horizontal seismic coefficients,are treated as random variables.The effects of these parameter uncertainties on the failure probability and sensitivity indices are discussed.In addition,the effects of weak layer position,the middle layer thickness and quality,the tunnel diameter,the parameters correlation,and the seismic loadings are investigated,respectively.The results show that the layer distributions significantly influence the tunnel face probabilistic stability,particularly when the weak rock is present in the bottom layer.The efficiency of the proposed ULT-PCK-MA is validated,which is expected to facilitate the engineering design and construction.

Study on Rollover Index and Stability for a Triaxle Bus

Vehicle rollover, and its resulting fatalities, is an actively researched topic especially for multi-axle vehicles in the field of vehicle dynamics and control. This paper first presents a new rollover index for a triaxle bus to accurately evaluate its rollover possibility and then discusses the influence laws of the vehicle rollover dynamics to explore the mechanism of its stability. First, a six degree of freedom rollover model of the triaxle bus is developed, including lateral, yaw, roll motion of the sprung mass of the front/rear axle, and roll motion of the unsprung mass of the front/rear axle. Next, some key parameters of the vehicle rollover model are identified. A new rollover index is deduced according to the basics of vehicle dynamics, to predict vehicle rollover risk for the triaxle bus, which is verified by TruckSim. Furthermore, the influence laws of vehicle rollover dynamics by vehicle parameters and road parameters are discussed based on the simulation results. More importantly, the results show that the new method of modeling can precisely describe the rollover dynamics of the studied bus, and the proposed new index can e ectively evaluate the rollover possibility. Therefore, this study provides a theoretical basis to improve anti-rollover ability for triaxle buses.

基于Global Stability Index(GSI)理论的水煮笋软罐头货架期预测

应用食品货架期预测新方法—Global Stability Index(GSI)进行水煮笋软罐头基于综合品质指标的保质期预测。基于恒温加速实验测定分析产品于23、33、43℃储藏温度下的品质变化规律,以色泽、可溶性蛋白质和维生素C作为水煮笋的关键质量指标,应用GSI理论描述产品基于多指标的综合劣变过程,获得不同温度下GSI值的变化趋势。结果表明,水煮笋软罐头GSI值的下降符合零级反应动力学。使用阿伦尼乌斯方程建立GSI货架期预测模型,并表征模型参数,计算出20℃下产品的保质期约为186d。经过理论预测与实验对比,得到的GSI值相对误差在22%以下,证明了该货架期预测方法的可靠性。

The stability safety factor calibration based on the reliability index

When the bridge structure stability safety factor of the first type is 4, the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type, the stability safety factor of the first type is taken as 4, and the first order reliability method is used to program and calculate the reliability index. Then, the load effect under the stability reliability index cal- culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above, parameter analysis of the stable critical loads of two types is made, and the in- fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state; when the stability safety factor of the first type is 4, but the structure has the collapse of the second type, the reliability index cannot be ensured to reach the target reliability index under certain condi- tions.

Global instability index as a crystallographic stability descriptor of halide and chalcogenide perovskites

Crystallographic stability is an important factor that affects the stability of perovskites.The stability dictates the commercial applications of lead-based organometal halide perovskites.The tolerance factor(t)and octahedral factor(μ)form the state-of-the-art criteria used to evaluate the perovskite crystallographic stability.We studied the crystallographic stabilities of halide and chalcogenide perovskites by exploring an effective alternative descriptor,the global instability index(GII)that was used as an indicator of the stability of perovskite oxides.We particularly focused on determining crystallographic reliability by calculating GII.We analyzed the bond valence models of the 243 halide and chalcogenide perovskites that occupied the lowest-energy cubic-phase structures determined by conducting the first-principles-based total energy minimization calculations.The decomposition energy(ΔHD)reflects the thermodynamic stability of the system and is considered as the benchmark that helps assess the effectiveness of GII in evaluating the crystallographic stability of the systems under study.The results indicated that the accuracy of predicting thermodynamic stability was significantly higher when GII(73.6%)was analyzed compared to the cases when t(55%)andμ(39.1%)were analyzed to determine the stability.The results obtained from the machine learning-based data mining method further indicate that GII is an important descriptor of the stability of the perovskite family.

Assessment of Groundwater Stability Using Corrosion and Scaling Tendency Indices on Selected Springs in the Manga Region in Nyamira County, Kenya

We present the result of groundwater stability assessment on three major springs in the Manga region in Nyamira County found in Kenya in 2018. These springs are Kiangoso (SP1), Kerongo (SP2) and Tetema (SP3). The corrosion and scaling tendency indices were obtained using the Langelier saturation index (LSI), Ryznar stability index (RSI), and Puckorius scaling index (PSI). The LSI values obtained for SP1, SP2, and SP3 are −3.93, −4.71, and −4.17, respectively, while using RSI, the values obtained for SP1, SP2, and SP3 are 14.15, 14.53, and 13.74, respectively. Using PSI, the values of SP1, SP2, and SP3 are 5.58, 5.45, and 5.58, respectively. From the interpretation of the indices, the groundwater from the three springs in the Manga region using LSI and RSI showed intolerable corrosion;hence, it is unlikely to scale as obtained from PSI.

Stability Analysis of Nonlinear Models of Nose Landing Gear Shimmy

Shimmy can reduce the service life of the nose landing gear, affect ride comfort, and even cause fuselage damage leading to aircraft crashes. Taking a light aircraft as the research object, the torsional freedom of landing gear around strut axis and lateral deformation of tire are considered. Since the landing gear shimmy is a nonlinear system, a nonlinear mechanical model of the front landing gear shimmy is established. Sobol index method is proposed to analyze the influence of structural parameters on the stability region of the nose landing gear, and Routh-Huritz criterion is used to verify the reliability of the analysis results of Sobol index method. We analyse the effect of torsional stiffness of strut, caster length, rated initial tire inflation pressure, rake angle, and vertical force on the stability region of theront landing gear. And the research shows that the optimization of the torsional stiffness of the strut and the caster length of the nose landing gear should be emphasized, and the influence of vertical force on the stability region of the nose landing gear should be paid attention to.

Correlation of coronary CTA calcification score with serum inflammatory factors and plaque stability-related indexes in patients with coronary heart disease

Objective: To investigate the correlation of coronary CTA calcification score (CACS) with serum inflammatory factors and plaque stability-related indexes in patients with coronary heart disease. Methods: A total of 228 patients with possible coronary heart disease who were examined in this hospital between November 2014 and March 2017 were selected, and the CACS levels as well as the serum contents of inflammatory factors and plaque stability indexes in patients with different lesions were determined. Pearson test was used to assess the correlation between CACS level and disease severity in patients with coronary heart disease. Results: The CACS level of triple vessel disease group was higher than that of double vessel disease group and single vessel disease group, and the CACS level of double vessel disease group was higher than that of single vessel disease group;serum sICAM-1, IL-6, IL-18, CRP, PTX3, Lp-PLA2 and Cat K contents were higher than those of double vessel disease group and single vessel disease group;serum sICAM-1, IL-6, IL-18, CRP, PTX3, Lp-PLA2 and Cat K contents of double vessel disease group were higher than those of single vessel disease group;serum Cys C content of triple vessel disease group was lower than that of double vessel disease group and single vessel disease group, and serum Cys C content of double vessel disease group was lower than that of single vessel disease group. Pearson test showed that the CACS level in patients with coronary heart disease was directly correlated with serum contents of inflammatory factors and plaque stability indexes. Conclusion: The CACS levels in patients with coronary heart disease increase with the aggravation of disease, and the specific CACS level is directly correlated with the degree of inflammatory response and the stability of the plaques.

Global Stability Index方法在大骨鸡保质期预测中的应用

目的:建立了基于全面稳定性指数(global stability index,GSI)理论预测庄河大骨鸡保质期的新方法。方法:基于恒温加速实验,测定大骨鸡于4、10、20、30℃储藏温度下的感官、汁液流失率、菌落总数和挥发性盐基氮变化规律,建立大骨鸡GSI保质期预测模型。结果:计算得到的GSI值满足零级动力学模型。活化能和指前因子分别为25.52 kJ/mol和11027。GSI实验值和预测值相对误差绝对值在10%范围内。通过GSI模型预测,获得大骨鸡在4、10、20、30℃下的保质期分别为5.9、4.7、3.2、2.3 d。结论:建立的GSI预测模型在4~30℃储藏温度范围内能够有效预测大骨鸡的新鲜度。

The stability indexes of branched airflow of ventilation network in coal mine

The stability of branched airflow of ventilation network is guarantee of safety in production of coal mine. Two indexes which stand for the stability of branches of ventilation network in coal mine were put forward in this paper, that are airflow intensity and sta- bility index of branched airflow, The airflow stability of working place was divided into different grade according to the stability index. The conclusion has great significance for safety in production of coal mine.

Utilizing Stability Index Tracing for Precise Load Buses Identification in Load Shedding Problem

This paper proposes a new approach for suitable load buses identification via stability index tracing in performing corrective load shedding. The proposed identification technique is called the Fast Voltage Stability Index Load Tracing (FVSI-LT). By implementing a power tracing algorithm, a group of major contributors on the stress experienced by a power system is able to be precisely identified by a system operator (SO) based on the traced values of FVSI. To be precise, the traced FVSI via FVSI-LT can be used to form a ranking list indicating the priority of buses committed for shedding purpose. After designing a Fuzzy Inference System (FIS) for deciding the allowable load powers to be shed and performing experiment on IEEE 57-Bus reliability test system (RTS), it is revealed that the ranking list provided by FVSI-LT results to the most consistent improvement in terms of voltage stability and losses minimization.

A multi-index coupling system of ice slope stability and its application

Based on the Simplified Bishop Method, the minimum safety factor of ice slope both with and without tension cracks is calculated in combination with triaxial compression tests. It is found that there exists a critical depth for each crack. Then, factors influencing ice slope stability such as slope ratio, slope height, ice cohesion, internal friction angle, unit weight and temperature were analyzed. Meanwhile, a regression equation between the aforementioned factors and safety factor is obtained, with which sensitivity analysis is carried out. The performance function is built in combination with random distribution of physical and mechanical parameters to analyze the reliability index. The Advanced First Order Second Moment Method is employed on the solution to the perfor- mance function. The one-way coupling system of ice slope stability is therefore formed based on safety factor and reliability index. Finally, an illustrated example of ice slope is provided, which shows that failure probability is relatively high, up to 6.18%, alt- hough safety factor is 2.77. Thus, it is objective and reasonable to apply the coupled system method to the slope stability rating.

Asymptotic Evaluations of the Stability Index for a Markov Control Process with the Expected Total Discounted Reward Criterion

In this work, for a control consumption-investment process with the discounted reward optimization criteria, a numerical estimate of the stability index is made. Using explicit formulas for the optimal stationary policies and for the value functions, the stability index is explicitly calculated and through statistical techniques its asymptotic behavior is investigated (using numerical experiments) when the discount coefficient approaches 1. The results obtained define the conditions under which an approximate optimal stationary policy can be used to control the original process.

Machine Learning for Hybrid Line Stability Ranking Index in Polynomial Load Modeling under Contingency Conditions

In the conventional technique,in the evaluation of the severity index,clustering and loading suffer from more iteration leading to more com-putational delay.Hence this research article identifies,a novel progression for fast predicting the severity of the line and clustering by incorporating machine learning aspects.The polynomial load modelling or ZIP(constant impedances(Z),Constant Current(I)and Constant active power(P))is developed in the IEEE-14 and Indian 118 bus systems considered for analysis of power system security.The process of finding the severity of the line using a Hybrid Line Stability Ranking Index(HLSRI)is used for assisting the concepts of machine learning with J48 algorithm,infers the superior affected lines by adopting the IEEE standards in concern to be compensated in maintaining the power system stability.The simulation is performed in the WEKA environment and deals with the supervisor learning in order based on severity to ensure the safety of power system.The Unified Power Flow Controller(UPFC),facts devices for the purpose of compensating the losses by maintaining the voltage characteristics.The finite element analysis findings are compared with the existing procedures and numerical equations for authentications.

Investigation of Connecting Wind Turbine to Radial Distribution System on Voltage Stability Using SI Index and λ - V Curves

The growth of wind energy penetration level in distribution system raises the concern about its impact on the operation of the power system, especially voltage stability and power loss. Among the major concerns, this paper studied the impact of connecting wind Turbine (WT) in radial distribution system with different penetration levels and different power factor (lead and lag) on power system voltage stability and power loss reduction. Load flow calculation was carried out using forward-backward sweep method. The analysis proceeds on 9- and 33-bus radial distribution systems. Results show that voltage stability enhancement and power loss reduction should be considered as WT installation objective.

Changes in plaque stability, cell apoptosis and coagulation indexes after patients with unstable angina pectoris accept adjuvant salvianolate therapy

Objective:To investigate the effect of adjuvant salvianolate therapy on plaque stability, cell apoptosis and coagulation indexes in patients with unstable angina pectoris.Methods: 92 patients with unstable angina pectoris treated in our hospital between May 2011 and August 2015 were collected, and after the treatment process and auxiliary examination results were retrospectively analyzed, they were divided into the control group (n=45) who accepted conventional treatment and the observation group (n=47) who accepted adjuvant salvianolate treatment. Before and after treatment, diasonograph was used to evaluate the plaque stability parameters of two groups of patients;ELISA was used to detect apoptosis-related molecule levels;immunoturbidimetry was used to detect blood coagulation indexes.Results: Before treatment, differences in plaque stability parameters, cell apoptosis molecules and coagulation indexes were not statistically significant between two groups of patients (P>0.05). After treatment, the plaque stability parameters plaque thickness, enhanced intensity, rise time and time to peak of observation group were significantly lower than those of control group (P<0.05);serum sFas, sFasL, fibrinogen (Fib), platelet (PLT), and D-Dimer (D-D) levels of observation group were significantly lower than those of control group while Bcl-2, prothrombin time (PT) and activated partial thromboplastin time (APTT) levels were significantly higher than those of control group (P<0.05).Conclusions: Adjuvant salvianolate treatment can increase the plaque stability, also inhibit myocardial cell apoptosis and improve the coagulation function in patients with unstable angina pectoris.

ANALYSIS OF TIPOVER STABILITY FOR NOVEL SHAPE SHIFTING MODULAR ROBOT

A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robot＇s tipover problem are analyzed, stability pyramid and tipover stabil-ity index are proposed to globally determinate the mobile robot＇s static stability and dynamic stability. The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robot＇s tipover stability, especially for the reconfigurable or shape shifting modular robot. Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type configuration has the best stability. Both simulation and experiment provide a valid reference for the reconfigurable robot＇s potential application.

Experimental study on stability of sunken large diameter cylindrical structure on sandy seabed during construction period

A systematic experimental research work is done for the stability of sunken large diameter cylinder during construction period. It is the first research that gives the method for assessing the stability of the larger diameter cylindrical structure, a set of values is derived also for the critical stability indices of the large diameter cylinder sunken to the sandy seabed.

Network Structure-Based Critical Bus Identification for Power System Considering Line Voltage Stability Margin

Voltage security assessment of power system is an important and all-inclusive aspect of power system operation and preventive control actions. Fast and accurate detection of critical components of the power system is one essential approach for preventing the occurrence of voltage collapse phenomenon. Over the years, several approaches for voltage collapse point identification and prevention have been widely studied using the continuous power flow approach, minimum singular value of eigenvalues, Jacobian matrices, and power transfer concept. In this work, critical node (bus) identification based on power system network structure is proposed. In this approach, the power system is treated as a multidimensional graph with several nodes (buses) linked together by the transmission lines. An improved line voltage stability margin estimator which is based on active and reactive power changes in a power system is used as the weight of each transmission line and an adaptation of the degree of centrality approach is used to determine the criticality of the system buses. A comparative analysis with other bus voltage stability indices is presented to test the suitability of the proposed approach using the IEEE 14, 30, 57 and 118 bus test systems.