Search

Taking the weakly cemented sandstone of Ordos, China, as the research object, the evolution law between the relative stress of weakly cemented sandstone and the multiparameters of the acoustic emission under different dry-wet cycles was explored, and the critical failure identification mode of weakly cemented sandstone under dry-wet cycle was established. The results show that as the number of dry-wet cycles increases, the wave velocity loss rate gradually increases. Overall, the longitudinal wave loss rate is larger than the shear wave loss rate, indicating that the longitudinal wave is more sensitive to the degradation of weakly cemented sandstone. With an increase in the number of dry-wet cycles, the crack is mainly caused by the main crack penetration failure, and the secondary crack is significantly reduced. The fractal dimension decreases with an increase in the dry-wet cycles and reaches its maximum at 0 dry-wet cycles, which means that 0 dry-wet cycles witness the most complex morphology of fractures within the weakly cemented sandstone. This finding indicates that the dry-wet cycle inhibits the generation and expansion of fractures. The event rate appears to be close to 0 before the rupture, and then the platform oscillates, followed by a sudden increase. The acoustic emission b value is relatively high during the initial stage and then decreases, which is the initial damage process. The elastoplastic phase rises again, the peak stage decreases rapidly, and the weakly cemented sandstone undergoes unstable damage. The change in the acoustic emission entropy value is exactly the opposite of the b value change law. When the weakly cemented sandstone reaches the critical failure state under different dry-wet cycles, the relative stress value is 95%. The test results provide new methods and a basis for the damage evolution mechanism and fracture prediction of weakly cemented sandstone under dry-wet cycles. [ABSTRACT FROM AUTHOR]

The political history of medieval China is written primarily on the basis of official records produced at centers of political power by victors in the preceding trans-dynastic war. With the help of alternative sources, one can hope to challenge the triumphalist and teleological narrative imbedded in these records. In this article, I use documents preserved in the Dunhuang "library cave" to uncover a failed attempt to establish a regional state with imperial pretensions in Dunhuang immediately after the fall of the Tang. This kind of political regionalism seen in Dunhuang is also found in several other post-Tang states in Sichuan and Guangdong. My investigation of their similarities exposes the teleological nature of the conventional framework of "Five Dynasties and Ten Kingdoms," and demands that we rethink the political history of China after the fall of the Tang. [ABSTRACT FROM AUTHOR]

In the vast inland areas of China, more than 3 million bridges have been built to connect the remote mountainous areas and also to make up the urban transportation networks. For these bridges, reinforced concrete is the most widely adopted material in construction. Unlike the offshore bridges subjected to chloride-induced corrosion, the inland bridges have been constantly threatened by atmospheric carbonation-induced corrosion. The inland areas of China are earthquake-prone regions where several major seismic events occurred in recent years. To investigate the seismic vulnerability of inland bridges subjected to atmospheric carbonation-induced corrosion, the time-dependent characteristics of carbonation were analyzed based on an illustrative cable-stayed bridge, and the time-dependent damage states of bridge components during earthquakes were identified through the material strains of reinforcing steel and concrete. A life-cycle fragility assessment method was proposed and was used to establish the time-dependent seismic fragility curves of the illustrative cable-stayed bridge at the component and system levels. Based on the time-dependent fragility analysis, the macro identification for the seismic damage to bridge system under each damage state and its influence on traffic and repair levels were discussed, the damage sequences of bridge components for different damage states were predicted, and the application strategies of the prediction for components' damage sequences at various service periods were introduced. The research shows that the stirrups tend to be corroded first, leading to rapid decreases of the characteristic strain values of the confined core concrete; and the longitudinal reinforcement experiences very slight corrosion during the bridge's service life. The atmospheric carbonation-induced corrosion increases significantly the damage probabilities of the various bridge components, and consequently change their damage sequences at different damage states. However, the carbonation-induced corrosion does not change the CDPs (complete damage points) and MDPs (maximum damage points) of various bridge components. The bridge system is vulnerable during earthquakes and significantly affected by material degradation. Within the design service life, the damage probabilities of the bridge system can be increased by 0.5620 by the carbonation-induced corrosion, the PGAs (peak ground accelerations) corresponding to CDPs can be decreased by 0.1 g, and the MDPs of the failure state can gradually convert to the CDPs. It is possible to predict the damage sequences of the bridge components during earthquakes on the basis of seismic fragility analysis for different service periods of the bridge, based on which the corresponding maintenance and retrofit strategies can then be determined to protect the bridge against possible earthquakes, and the costs can be reduced. [ABSTRACT FROM AUTHOR]

The Taiyuan Formation limestone aquifer and Ordovician limestone aquifer are widely distributed in the coal seam floor of coal measures in North China; the water hazard safety problem of the stope floor under the influence of mining is very prominent. The risk of the water inrush from the coal seam floor is closely related to the degree of full exploitation, so it is necessary to study the stability of the stope floor under aquifer conditions, especially the influence of the working face length effect on floor stability. Through numerical simulation of water-rock coupling action, the mine pressure behaviors of the water-resisting floor under different face lengths were analyzed based on the measured formation permeability coefficient. The Fish program was used to adjust rocks entering the plastic failure state into a strain softening model to investigate the influence of the face length effect, the damage degree of the water-resisting floor, and the morphology and deformation bearing capacity of the failure zone. The results show the following: (1) the face length effect is one of the main influence factors of the failure mode and failure degree of surrounding rocks in the stope; (2) as the face length increases, the obvious pressure relief zone of surrounding rocks presents a staged change, and the obvious pressure relief zone at the seam roof and floor is in an obvious "reverse saddle shape"; (3) the closer to the seam floor, the more remarkable the rock softening characteristic because of the compaction action of gangues caving from the roof; and (4) the rock mass close to the seam floor undergoes local tensile failure, and the water-resisting floor near the coal wall at two sides mainly bears compaction-shear action, leading to compression-shear failure of the rock mass at the floor and formation of water-conducting fractures. The study results can provide a reference for taking precautionary measures of safety mining above a confined aquifer. [ABSTRACT FROM AUTHOR]

The source of greatest energy released during an earthquake has not yet been determined. Considering the basic characteristics of frequent occurrence of strong earthquakes at the intersection of two sets of crustal rupture zones, a model for energy analysis by taking a soft anisotropic body as the center was established and the calculated method of seismic energy was proposed on the basis of butterfly failure theory. From the viewpoint that the surrounding rocks of a soft anisotropic body were subjected to plastic failure resulting in the change in energy released, the authors numerically analyzed the influence of the presence of a soft anisotropic body on energy accumulation in surrounding crustal rocks during an earthquake, and discussed the general law of natural earthquake triggering. Based on the geological background of the epicenter location of the Ludian ML6.5 earthquake in the southwestern part of China, the variation law of source energy and distribution characteristics of earthquakes with or without a soft anisotropic body was further analyzed. The calculated results showed that the soft anisotropic body in the crust redistributed the stress in the surrounding rock mass and formed the stress concentration around the soft anisotropic body. With the increase of compression and tensile structural stress, the rock masses around soft anisotropic body were subjected to plastic failure leading to an accumulation of energy with the epicenter of butterfly-shaped damage zone, which was the main source of seismic energy. The soft anisotropic body changed the energy accumulation characteristics of the surrounding rock mass exponentially, and the butterfly-shaped energy concentration area was formed during the evolution of butterfly plastic damage in the surrounding rock of the soft anisotropic body, indicating the transition from the steady state to unsteady state of energy concentration. The range of plastic failure and the state of accumulated energy of rock mass around the soft anisotropic body determined the magnitude of earthquakes. In the period of intense expansion of the butterflyshaped failure, minor stress disturbances can cause the catastrophe of the whole energy system of surrounding rock and trigger large-magnitude natural earthquakes. [ABSTRACT FROM AUTHOR]

Based on the reliability theory, this paper gave the expression of the "failure-non failure"state of the urban road traffic unit and the traffic network and analyzed the change law of their states; analyzed the time distribution of the link unit and the traffic network from the observed starting point t0 to the "first failure state". Based on these, it deduced the failure probability, average failure time, failure rate and conditional length of failure time of the urban road unit and traffic network, it also gave the method of model calibration. It took a road traffic network that composed of five road units in a core city of China by an example, fitted and checked the first failure time of the road units and the traffic network, also compared the model calculation results with the actual observation results. The results show that it is better to use logarithmic normal distribution to fit the first failure time, and the calculation results of the model are very close to the actual observation results, which shows that the model has good practicability. [ABSTRACT FROM AUTHOR]

This article examines religious freedom in the People’s Republic of China (PRC) using critical frame analysis of state and civil society organisations’ (CSOs) policy discourse associated with the United Nations (UN) Universal Periodic Review (UPR). The findings show how indigenous Chinese CSOs’ input to the UPR is limited. Their voice is muted, some merely mirror the rhetoric of the ruling Chinese Communist Party (CCP). In contrast, international CSOs are highly critical of what they see as state failure to uphold religious freedom. The analysis reveals a significant disjuncture between the policy discourse of international CSOs and the CCP. The former’s discourse is framed in terms of: denial of rights, imprisonment, legal failings, (re-)education, torture, and persecution. In the absence of enforcement mechanisms, CCP input to the UPR can be seen as part of a process of legitimation and performativity; allowing the ruling elite to afford primacy to what it dubs ‘a framework of socialism with Chinese characteristics’ at the expense of religious freedoms. [ABSTRACT FROM AUTHOR]

The Zhouqu County of Gansu Province in northwestern China is a geological hazard-prone area with frequent landslide and debris flow events. As a recent example, the Jiangdingya landslide, a smaller landslide within the larger ancient Nanyu landslide, was reactivated and partially collapsed to block the Bailong River near the Nanyu Township on 12 July 2018. Previous studies have shown that heavy rainfall is the major triggering factor of the failure event, but the spatio-temporal pattern of surface displacements of the landslide remains unknown due to a lack of in-situ measurements on the slope. In this study, we retrieved the surface displacements of the Nanyu landslide before the slope failure event using time-series Synthetic Aperture Radar Interferometry (InSAR) analysis of Sentinel-1 and ALOS-2 PALSAR-2 data. Our results show that the ancient Nanyu landslide has been in an unstable state prior to the failure event. To investigate the spatial patterns in displacement, we inverted a quasi three-dimensional (3D) surface displacement field using multi-orbit InSAR measurements combined with the surface parallel flow model, which showed a significant spatial heterogeneity in displacement patterns across the ancient landslide. In particular, a sign of local reactivation was observed on the upper slopes, which might be related to recent road construction activities. Furthermore, the detectability of unstable slopes near the Nanyu landslide with Sentinel-1 and ALOS-2 PALSAR-2 observations was analyzed to deepen our knowledge on the optimal choice of SAR data for geohazards detection and monitoring. • Historic displacements of the Nanyu landslide measured by time-series InSAR. • Multi-track InSAR combined with surface parallel flow model to retrieve 3D motions. • A complex spatial pattern of landslide movement revealed by 3D displacement field. • Slope-facing geometry found to be more suitable to detect active deforming landslides. • Rainfall and human activity inferred as major driving factors for slope deformation. [ABSTRACT FROM AUTHOR]

In North Korea, the upcoming leadership transition in the Kim Jong-il regime will be a precarious time for the Kim family’s hold on power. A collapse of the North Korean government could have several dangerous implications for East Asia, including “loose nukes,” a humanitarian disaster, a regional refugee crisis, and potential escalation to war between China and the United States. To respond to a collapse and these problems, neighboring countries may perform several military missions to stabilize North Korea. These include the location and securing of North Korean weapons of mass destruction, stability operations, border control, conventional disarmament, and combat/deterrence operations. Assuming that collapse occurs in a relatively benign manner, military missions to stabilize North Korea could require 260,000 to 400,000 troops. If collapse occurs after a war on the peninsula, or if it sparks civil war in North Korea, the number of missions -- and their requirements -- would grow. Because of the size and complexity of these missions, and because of the perils associated with mismanaging them, advance and combined planning is essential. Combined planning should include those actors (e.g., China, South Korea, and the United States) that could otherwise take destabilizing action to protect

Rising economies including China, the United Arab Emirates, Brazil, Korea, India, Kuwait and Saudi Arabia are subtly changing the rules of foreign aid with profound consequences for the role of multilateral institutions and conditionality. Fears abound that this new aid is bolstering rogue states, fuelling corruption, and increasing the debt burdens of poor countries. This article critically assesses these arguments before dissecting the attractions of emerging donors' aid against a background of established donors' failure to deliver on promises to increase aid, reduce conditionality, better coordinate and align aid efforts, and reform the aid architecture. It argues that a silent revolution is taking place whereby the emerging donors are not overtly attempting to overturn the rules of multilateral development assistance, nor to replace them. Rather, by quietly offering alternatives to aid-receiving countries, they are weakening the bargaining position of western donors. The resulting tensions underscore the urgency of reforming the multilateral aid system. [ABSTRACT FROM AUTHOR]

• A failure criterion model in the strain space was established by the convention method based on the generalized Hooke's law. • The linearized calculation model of resilient modulus was established by the resilient modulus tests in complex stress state. • The strain failure criterion model considering the effect of stiffness was established. In order to reveal the effect of complex stress state on the characteristics of strength and stiffness of asphalt mixture, the self-developed double confining pressure triaxial test method was used in this study. The one-time failure and resilient modulus tests in complex stress state were carried out on the SMA-13 and AC-13 asphalt mixtures widely used in China's asphalt pavement, especially in the combined tensile-compressive stress state. The failure principal stress of material and its stress-strain data under the step loading condition were obtained. The calculation model of resilient modulus in complex stress state and the failure criterion I 1 - J 2 in the principal stress space were established. On this basis, based on the generalized Hooke's law, a three-dimensional strain failure criterion model for asphalt mixture considering the effect of stiffness was also established by the conversion method. The research results can provide experimental and theoretical support for the reasonable selection and resistance calculation of material parameters of asphalt mixture in complex stress state. [ABSTRACT FROM AUTHOR]