The highest volcano in Mexico,at the same time the third largest mountain in North America(Citlaltépetl,5610 m a.s.l.),is home to the largest glacier in the country.Because of the extinction of the Popocatép...The highest volcano in Mexico,at the same time the third largest mountain in North America(Citlaltépetl,5610 m a.s.l.),is home to the largest glacier in the country.Because of the extinction of the Popocatépetl glacier(5500 m a.s.l.)caused by eruptive activity,and the almost disappearance of the Iztaccíhuatl glaciers(5220 m a.s.l.)due to the lower elevation of the mountain,the Glaciar Norte of Citlatépetl has been the only glacier that has shown a certain degree of stability as a response to the altitude in which it is located.However,as occurs in almost all glaciers on the planet,the retreat of its glacier terminus has been continuous.Furthermore,during the last years the thickness of its upper part began to decrease rapidly until its bedrock was exposed for the first time in 2019.Due to its ecosystem importance and because it is the main glacier in Mexico,as well as the only one in the world located at latitude 19°N,in this work its current dimensions are updated,as well as the local climatology that governs the current state of the glacier is pointed out.The study was based on the analysis of high-resolution Sentinel-2 optical images,as well as through Sentinel-1 SAR images,with the support of climatological information from the study area.Therefore,the outcropping of the bedrock in the accumulation zone and the consequent horizontal retreat of the upper part of the glacier are documented;at the same time,the decrease in the thickness of the ice along it is noted.The rocky outcrop in the accumulation zone suggests that the flow dynamics of the ice towards the ablation zone will be considerably less,accelerating the retreat of the glacier terminus.Finally,the ascent of the glacial front to 5102 m a.s.l.and the modelled altitude of the equilibrium line to 5276 m a.s.l.are reported as a warning signal in terms of snow catchment and mass balance;likewise,the decrease of 23%of its surface is also indicated regarding the surface reduction monitoring that has been done until 2017.These findings may indicate that the future of this glacier is related to its possible extinction sooner than previously thought,with severe environmental consequences,especially in terms of the provision of drinking water for thousands of inhabitants of the slopes of the volcano.This research is expected to help reflect on the impacts of current climate variability and at the same time serve as a reference for the tropical glaciers on the planet.展开更多
AIM: To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma (HCC). METHODS: The data of 14 968 patients who had ultrasonography (US) for chronic liver disease...AIM: To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma (HCC). METHODS: The data of 14 968 patients who had ultrasonography (US) for chronic liver diseases were collected into a database program from June 1995 to June 2005. The risk factors for HCC were also studied. A total of 6089 patients who had repeated US were enrolled, 264 patients were diagnosed with HCC during follow-up (mean, 39 mo). RESULTS: The detection rate of small HCC (≤ 3 cm in diameter) was 67.7%. The tumor size detected by screening at the intervals of 6 mo was significantly smaller than that at longer intervals. Only 29.3% of HCC patients had an elevated serum alpha fetoprotein (AFP) level above 400 ng/mL. The risk of HCC development during follow-up was higher in patients with liver cirrhosis (10.9%) and hepatitis C (9.0%) than in patients with chronic hepatitis (4.2%), hepatitis B (4.9%) and non-B, non-C hepatitis (NBNC, 3.9%). CONCLUSION: US screening at a interval of 6 mo is beneficial to high-risk patients over 40 years old and the early detection of HCC prolongs survival.展开更多
Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies ...Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types (5 sites in grassland, 3 in woodland and 1 in shrubland) in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics (including root average diameter, root length density, root surface density and root biomass density), but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process (8-50 years).展开更多
AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other ...AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other therapeutic regimens without success.METHODS: Open cohort study which included patients with peptic ulcer who had previously been treated unsuccessfully with one or more eradication regimens.The therapeutic regimen consisted of 20 mg omeprazole,240 mg colloidal bismuth subcitrate,1000 mg amoxicillin,and 200 mg furazolidone,taken twice a day for 7 d.Patients were considered as eradicated when samples taken from the gastric antrum and corpus 12 wk after the end of treatment were negative for Helicobacter pylori (H pylori) (rapid urease test and histology).Safety was determined by the presence of adverse effects.RESULTS: Fifty-one patients were enrolled.The eradication rate was 68.8% (31/45).Adverse effects were reported by 31.4% of the patients,and these were usually considered to be slight or moderate in the majority of the cases.Three patients had to withdraw from the treatment due to the presence of severe adverse effects.CONCLUSION: The association of bismuth,furazolidone,amoxicillin and a proton-pump inhibitor is a valuable alternative for patients who failed to respond to other eradication regimens.It is an effective,cheap and safe option for salvage therapy of positive patients.展开更多
Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have...Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered: the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling(superplume) systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that:(1) at the center half of the supercontinent, plume push stress is ~3 times larger than the stress induced by subduction retreat;(2) an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;(3) the extensional stress induced by subduction retreat concentrates on a ~600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.展开更多
AIM:Primary biliary cirrhosis (PBC) is a chronic, cholestatic disease of autoimmune etiology,the histology of which shows a destruction of the intrahepatic bile duct and portal inflammation. Ursodeoxycholic acid (UDCA...AIM:Primary biliary cirrhosis (PBC) is a chronic, cholestatic disease of autoimmune etiology,the histology of which shows a destruction of the intrahepatic bile duct and portal inflammation. Ursodeoxycholic acid (UDCA) is now used as a first-line drug for asymptomatic PBC (aPBC) because it is reported that UDCA decreases mortality and prolongs the time of liver transplantation.However, only 20-30% of patients respond fully to UDCA.Recently,lipoprotein-lowering agents have been found to be effective for PBC.The aim of this study was to examine the safety and efficacy of fenofibrate, a member of the fibrate class of hypolipidemic and anti-inflammatory agent via peroxysome proliferatory-activated receptor α,in patients with aPBC.METHODS:Fenofibrate was administered for twelve weeks in nine patients with aPBC who failed to respond to UDCA.UDCA was used along with fenofibrate during the study.The data from aPBC patients were analyzed to assess the biochemical effect of fenofibrate during the study.RESULTS: The serum levels of alkaline phosphatase (ALP)(285±114.8IU/L) and immunoglobulin M (IgM) (255.8±85.9mg/dl) significantly decreased to 186.9±76.2IU/L and 192.9±67.5mg/dL respectively, after fenofibrate treatment in patients with aPBC (P<0.05). Moreover,the titer of antimitochondrial antibody (AMA) also decreased in 4 of 9 patients with aPBC. No adverse reactions were observed in any patients.CONCLUSION:Fenofibrate appears to be significantly effective in treating patients with aPBC who respond incompletely to UDCA alone.Although the mechanism of fenofibrate on aPBC has not yet been fully clarified,combination therapy using fenofibrate and UDCA might be related to the anti-immunological effects, such as the suppression of AMA production as well as its antiinflammatory effect.展开更多
Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events su...Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events such as heavy rainfall,snowline retreating,great earthquake together with human activities,catastrophic landslides happened more frequently than before,resulting in large-scale casualties due to the increasing occurrences of rapid long-runout rock avalanches,especially in China.This paper presents some typical case histories related to the catastrophic landslides,including the Guanling rock avalanche,the Yigong rockslide-debris avalanche,the Wenchuan earthquake-induced landslides and the Danba landslide.They occurred in the last decade.Moreover,taking the Jiweishan catastrophic rockslide-fragment flow and the Yuhuangge landslide located in the new Wushan Town for examples,early-warning system and risk management on landslides are discussed in detail.展开更多
Both marginal fluctuation and areal change were used to detect the accurate dynamics of glacier change in the study area using Landsat MSS, ETM, SPOT HRV and topographic maps based on GIS. From 1963 to 1977, four of e...Both marginal fluctuation and areal change were used to detect the accurate dynamics of glacier change in the study area using Landsat MSS, ETM, SPOT HRV and topographic maps based on GIS. From 1963 to 1977, four of eight glaciers advanced, two of them retreated and another two kept stable, the glacier advanced generally. From 1977 to 1986, four of eight glaciers retreated and the others kept stable, but the retreated glaciers were those which advanced from 1963 to 1977. From 1986 to 2000, seven of eight glaciers retreated and only one glacier kept stable, the retreating velocity was 10-15 m/a. Glacier recession in this period became very fast and universal. From 1963 to 2000, the area of glaciers decreased from 5479.0 ha to 4795.4 ha, up to 12.5%. It is alarming that most of glacier retreats happened from 1986 to 2000. This was very consistent with change process of summer mean temperature in this region and global warming beginning in the 1980s.展开更多
Global warming triggers shrinking and thinning of glaciers worldwide,with potentially severe implications for human society.However,regional differences in glacier retreat and its relationship with climatic characteri...Global warming triggers shrinking and thinning of glaciers worldwide,with potentially severe implications for human society.However,regional differences in glacier retreat and its relationship with climatic characteristics have not been conclusively demonstrated.In this study,regional changes in global glaciers based on two primary features,area change and mass balance,were investigated on the basis of data collected from published research on glacier changes.Results show that during the period 1980—2015,the rate of global glacier area shrinkage was 0.18%per year and that of global glacier mass loss was 0.25 m w.e.per year.Retreat of glaciers located at low and middle latitudes was characterized by severe area shrinkage and mass loss.Correspondingly,in the Arctic,deglaciation was characterized by ice thinning due to a low area reduction but relatively high mass loss rate.However,glaciers in high southern latitudes were in a relatively stable status.High Mountain Asia exhibited the lowest rate of area shrinkage and mass loss among glaciers located at low and middle latitudes,and a slower rate of mass loss compared with the global average.Glaciers in the Tropical Andes exhibited the fastest rate of glacier area shrinkage(—1.6%per year),whereas Antarctic and Subantarctic glaciers showed the lowest rate(—0.11%per year).For mass balance,the most negative occurred at Southern Andes(—0.81 m w.e.per year),followed by Alaska(-0.74 m w.e.per year).Only the Antarctic and Subantarctic experienced small mass gain(0.04 m w.e.per year).High levels of correlation are found between the rates of glacier retreat and annual average temperature and annual total precipitation instead of their trends.The variability of the surface climate conditions in the glacier environment plays a key role in driving these regional differences in global glacier retreat.展开更多
Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic dec...Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.展开更多
Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The su...Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.展开更多
Inland lakes and alpine glaciers are important constituents of water resources in arid and semiarid regions. Understanding their variations is critical for both an accurate evaluation of the dynamic changes of water r...Inland lakes and alpine glaciers are important constituents of water resources in arid and semiarid regions. Understanding their variations is critical for both an accurate evaluation of the dynamic changes of water resources and the retrieval of climatic information. On the basis of earlier researches, this study investigated the growth of the Sayram Lake and the retreat of its water-supplying glaciers in the Tianshan Mountains using long-term sequenced remote sensing images. Our results show that over the past 40 years, the surface area and the water level of the lake has increased by 12.0±0.3 km<sup>2</sup> and 2.8 m, respectively, and the area of its water-supplying glaciers has decreased continuously since the early 1970s with a total reduction of about–2.13±0.03 km<sup>2</sup>. Our study has indicative significance to the research of regional climate change.展开更多
The glacier on the Yulong Mountain is one of the most important attractions in Lijiang, Yunnan, China. But it keeps retreating these years due to global warming, which is bound to influence regional tourism significan...The glacier on the Yulong Mountain is one of the most important attractions in Lijiang, Yunnan, China. But it keeps retreating these years due to global warming, which is bound to influence regional tourism significantly in Lijiang. This study estimates the effects of the glacier retreat of the Yulong Mountains on tourism there. Primary data were collected through a visitor survey including demographics, motives, lengths of stay, and opinions about each tourism resource from tourists to Lijiang, as well as questions about which scenic spot(s) they had visited or would visit, how much they expended per day during their visit and how their visiting behavior would be changed upon the hypothesis that the glacier would disappear. These data were used to analyze the proportion of the contribution of glacier to the tourism in Lijiang and estimate the impact of glacier on the regional tourism quantitatively. According to the survey, it could be concluded that three quarters of the tourists to Lijiang were interested in the Yulong Mountain glacier, indicating that the glacier possesses notable appeal for sightseeing tourists. The results of our analysis showed that about 689,013-1,508,247 tourists, accounting for 19.63-42.97 % of the total 3,510,000 domestic tourists to Lijiang in 2004, would not come to Lijiang in the absence of the glacier, resulting in a possible direct economic loss of 84,382,508-184,713,011 USD (viz. 700,374,824-1,533,117,993 RMB) and a markedly decrease in the attraction radius.展开更多
For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines.Studies showed that a miner on a pillar recovery section was at least three times more likely to be killed by ...For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines.Studies showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000 s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local stability.Global stability is addressed primarily through proper pillar design, and became a major focus after the2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:(1) leaving an engineered final stump, rather than extracting the entire pillar,(2) enhancing roof bolt support, particularly in intersections, and(3) increasing the use of mobile roof supports(MRS). A final component was an emphasis on better management of pillar recovery operations.This included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations,and hazard identification. As retreat mines have incorporated these elements into their roof control plans,it has become clear that pillar recovery is not ‘‘inherently unsafe." The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.展开更多
The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation met...The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.展开更多
Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal...Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered7 To help answer these questions, and to determine some of the relevant factors influencing the conditions of room and pillar (R & P) retreat min- ing entries, four consecutive R & P retreat panels were evaluated. This evaluation was intended to rein- force the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry. This paper details observations were made in four consecutive R & P retreat panels and the data were collected from an instrumentation site during retreat mining. The pri- mary focus was on the differences observed among the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the obse^ation and |ll^trumentation, numerical modeling was per- formed to evaluate the stress condi~!ons. Both the LaModel 3.0 and Rocscience Phase 2 programs were used to evaluate these four panels, The results of both models indicated a drastic reduction in the vertical stresses experienced in these panels due to the full extraction mining in overlying seams when compared to the full overburden load. Both models showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. These efforts provided two overarching conclusions concerning R & P retreat mine planning and execution. The first was that there are four areas that should not be overlooked during R & P retreat mining: topographic relief, multiple^seaPa stress relief, stress concentrations near the gob edge, and geologic changes in the immediate roof. The second is that in order to successfully retreat an R & P panel, a three-phased approach to the design and analysis of the panel should be conducted: the planning phase, evaluation phase, and monitoring phase.展开更多
The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the s...The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.展开更多
Based on the field surveys and repeated cross-profile observations combined with the comparison of many years’ topog-raphic maps,this study shows the spatial variability and varying patterns of coastal erosion along ...Based on the field surveys and repeated cross-profile observations combined with the comparison of many years’ topog-raphic maps,this study shows the spatial variability and varying patterns of coastal erosion along the west coast of the Taiwan Strait.Regional differentiation in the Meso-Cenozoic coastal tectonics determined the irregular coastline and geological background for large-scale coastal erosion distribution.The intensity of coastal erosion on the west side of the Taiwan Strait is mild in the northern region,severe in the central region and modest in the southern region.The beaches along the coast are mainly backed by dunes,sea-walls or cliffs.The dunes and beaches show periodic erosion and recovery along the coast adjacent to river mouths,while persistent retreat of frontal dunes and beaches tends to occur in other areas.The beach erosion occurs mainly in front of seawalls.Due to the low strength of the unconsolidated sediment the soft cliffs suffer the severest coastline recession.Sea level rise and river sediment discharge reduction are main causes of coastal erosion.Storm surge is common in the studied area and plays an important role in the progress of coastal erosion.Human activities including coastal constructions and sand mining also tend to interfere strongly with the balance of sediment budget in some coastal cells.展开更多
As the unprecedented global warming is under way, the glacier retreat is getting more and more serious. In the inland arid area of Northwest China, due to very scarce precipitation, where there is water, there are oas...As the unprecedented global warming is under way, the glacier retreat is getting more and more serious. In the inland arid area of Northwest China, due to very scarce precipitation, where there is water, there are oases. And the glacier melt water amounts to 22 % of the total direct supply of the inland river water and is of crucial importance to the survival and development of the oases. In this paper, using both the observed data and the previous research achievements of the glaciers in the inland valley of Northwest China where the oasis depending on the glacier is the only location suitable for human living, the authors describe the glacier retreat trend over the past half century, focusing on discussing the possible impact of the glacier retreat on the melt water runoff that is almost the only water resource efficient to nourish the oases. The authors find that even with increasing amount of water from the glacier with global warming, the water shortage is getting more and more serious and the environment is under a degrading way due to the accelerating economical development. The water shortage is bound to be more serious if the glacier retreat keeps on, especially after the glacier melt water is over its top for the degradedglacier scale. So suggestions are stressed in the end that a new water-saving pattern should be adopted in the area for a sustainable development due to the warming-up induced continuous glacier retreat.展开更多
The Chenab basin is located in northwest India and eastern Pakistan.Glaciers in Chenab basin,as local freshwater resources,are very important to the regional ecological environment and development.At the same time,SBA...The Chenab basin is located in northwest India and eastern Pakistan.Glaciers in Chenab basin,as local freshwater resources,are very important to the regional ecological environment and development.At the same time,SBAS InSAR can monitor the deformation of the ground for a long time,the monitoring accuracy can reach mm level,and can obtain the time series change of deformation,whcih provides a new idea and method for glacier detection.In this study,the deformation from SBAS InSAR was combined with glacial area data to study the glacial changes in Chenab Basin.Sentinel-1 and Landsat series images were used to obtain the deformation and change in the area of glaciers by SBAS InSAR and the semi-automated method.The results showed that glaciers in the Chenab basin retreated rapidly,especially in the past ten years.The glacier area decreased by 88.05 km^(2)in 1990~2000 and 118.86 km^(2) in 2000~2010,and the glacier area decreased by 236.01 km^(2) in 2010~2020,which was the largest rate of change of 9.49%.Moreover,glacial deformation decreased in 2020,and the deformation rate ranged from-146.3mm/a to 119.52 mm/a.Most glaciers had deformation rates between-50 mm/a and 50 mm/a.Influenced by precipitation and temperature,glacial deformation in the Chenab basin started to change in August,the maximum accumulation was 6,828.43mm,and the minimum ablation was-20,656.41 mm.展开更多
文摘The highest volcano in Mexico,at the same time the third largest mountain in North America(Citlaltépetl,5610 m a.s.l.),is home to the largest glacier in the country.Because of the extinction of the Popocatépetl glacier(5500 m a.s.l.)caused by eruptive activity,and the almost disappearance of the Iztaccíhuatl glaciers(5220 m a.s.l.)due to the lower elevation of the mountain,the Glaciar Norte of Citlatépetl has been the only glacier that has shown a certain degree of stability as a response to the altitude in which it is located.However,as occurs in almost all glaciers on the planet,the retreat of its glacier terminus has been continuous.Furthermore,during the last years the thickness of its upper part began to decrease rapidly until its bedrock was exposed for the first time in 2019.Due to its ecosystem importance and because it is the main glacier in Mexico,as well as the only one in the world located at latitude 19°N,in this work its current dimensions are updated,as well as the local climatology that governs the current state of the glacier is pointed out.The study was based on the analysis of high-resolution Sentinel-2 optical images,as well as through Sentinel-1 SAR images,with the support of climatological information from the study area.Therefore,the outcropping of the bedrock in the accumulation zone and the consequent horizontal retreat of the upper part of the glacier are documented;at the same time,the decrease in the thickness of the ice along it is noted.The rocky outcrop in the accumulation zone suggests that the flow dynamics of the ice towards the ablation zone will be considerably less,accelerating the retreat of the glacier terminus.Finally,the ascent of the glacial front to 5102 m a.s.l.and the modelled altitude of the equilibrium line to 5276 m a.s.l.are reported as a warning signal in terms of snow catchment and mass balance;likewise,the decrease of 23%of its surface is also indicated regarding the surface reduction monitoring that has been done until 2017.These findings may indicate that the future of this glacier is related to its possible extinction sooner than previously thought,with severe environmental consequences,especially in terms of the provision of drinking water for thousands of inhabitants of the slopes of the volcano.This research is expected to help reflect on the impacts of current climate variability and at the same time serve as a reference for the tropical glaciers on the planet.
文摘AIM: To evaluate the effectiveness of ultrasonographic screening for early detection of hepatocellular carcinoma (HCC). METHODS: The data of 14 968 patients who had ultrasonography (US) for chronic liver diseases were collected into a database program from June 1995 to June 2005. The risk factors for HCC were also studied. A total of 6089 patients who had repeated US were enrolled, 264 patients were diagnosed with HCC during follow-up (mean, 39 mo). RESULTS: The detection rate of small HCC (≤ 3 cm in diameter) was 67.7%. The tumor size detected by screening at the intervals of 6 mo was significantly smaller than that at longer intervals. Only 29.3% of HCC patients had an elevated serum alpha fetoprotein (AFP) level above 400 ng/mL. The risk of HCC development during follow-up was higher in patients with liver cirrhosis (10.9%) and hepatitis C (9.0%) than in patients with chronic hepatitis (4.2%), hepatitis B (4.9%) and non-B, non-C hepatitis (NBNC, 3.9%). CONCLUSION: US screening at a interval of 6 mo is beneficial to high-risk patients over 40 years old and the early detection of HCC prolongs survival.
基金supported by the National Natural Science Foundation of China(41571275)the Western Action Plan Project of the Chinese Academy of Sciences(KZCX-XB3-13)the Major Program of the National Natural Science Foundation of China(41790444/D0214)
文摘Soil erosion on the Loess Plateau of China is effectively controlled due to the implementation of several ecological restoration projects that improve soil properties and reduce soil erodibility. However, few studies have examined the effects of vegetation restoration on soil properties and erodibility of gully head in the gully regions of the Loess Plateau. The objectives of this study were to quantify the effects of vegetation restoration on soil properties and erodibility in this region. Specifically, a control site in a slope cropland and 9 sites in 3 restored land-use types (5 sites in grassland, 3 in woodland and 1 in shrubland) in the Nanxiaohegou watershed of a typical gully region on the Loess Plateau were selected, and soil and root samples were collected to assess soil properties and root characteristics. Soil erodibility factor was calculated by the Erosion Productivity Impact Calculator method. Our results revealed that vegetation restoration increased soil sand content, soil saturated hydraulic conductivity, organic matter content and mean weight diameter of water-stable aggregate but decreased soil silt and clay contents and soil disintegration rate. A significant difference in soil erodibility was observed among different vegetation restoration patterns or land-use types. Compared with cropland, soil erodibility decreased in the restored lands by 3.99% to 21.43%. The restoration patterns of Cleistogenes caespitosa K. and Artemisia sacrorum L. in the grassland showed the lowest soil erodibility and can be considered as the optimal vegetation restoration pattern for improving soil anti-erodibility of the gully heads. Additionally, the negative linear change in soil erodibility for grassland with restoration time was faster than those of woodland and shrubland. Soil erodibility was significantly correlated with soil particle size distribution, soil disintegration rate, soil saturated hydraulic conductivity, water-stable aggregate stability, organic matter content and root characteristics (including root average diameter, root length density, root surface density and root biomass density), but it showed no association with soil bulk density and soil total porosity. These findings indicate that although vegetation destruction is a short-term process, returning the soil erodibility of cropland to the level of grassland, woodland and shrubland is a long-term process (8-50 years).
文摘AIM: To establish the efficacy and safety of a 7-d therapeutic regimen using omeprazole,bismuth subcitrate,furazolidone and amoxicillin in patients with peptic ulcer disease who had been previously treated with other therapeutic regimens without success.METHODS: Open cohort study which included patients with peptic ulcer who had previously been treated unsuccessfully with one or more eradication regimens.The therapeutic regimen consisted of 20 mg omeprazole,240 mg colloidal bismuth subcitrate,1000 mg amoxicillin,and 200 mg furazolidone,taken twice a day for 7 d.Patients were considered as eradicated when samples taken from the gastric antrum and corpus 12 wk after the end of treatment were negative for Helicobacter pylori (H pylori) (rapid urease test and histology).Safety was determined by the presence of adverse effects.RESULTS: Fifty-one patients were enrolled.The eradication rate was 68.8% (31/45).Adverse effects were reported by 31.4% of the patients,and these were usually considered to be slight or moderate in the majority of the cases.Three patients had to withdraw from the treatment due to the presence of severe adverse effects.CONCLUSION: The association of bismuth,furazolidone,amoxicillin and a proton-pump inhibitor is a valuable alternative for patients who failed to respond to other eradication regimens.It is an effective,cheap and safe option for salvage therapy of positive patients.
基金supported by Australian Research Council Australian Laureate Fellowship grant to ZXL (FL150100133)by China’s Thousand Talents Plan (2015)+2 种基金NSFC41674098 to NZsupported by resources provided by the High-performance Computing Platform of Peking Universitythe Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia
文摘Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered: the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling(superplume) systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that:(1) at the center half of the supercontinent, plume push stress is ~3 times larger than the stress induced by subduction retreat;(2) an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;(3) the extensional stress induced by subduction retreat concentrates on a ~600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.
文摘AIM:Primary biliary cirrhosis (PBC) is a chronic, cholestatic disease of autoimmune etiology,the histology of which shows a destruction of the intrahepatic bile duct and portal inflammation. Ursodeoxycholic acid (UDCA) is now used as a first-line drug for asymptomatic PBC (aPBC) because it is reported that UDCA decreases mortality and prolongs the time of liver transplantation.However, only 20-30% of patients respond fully to UDCA.Recently,lipoprotein-lowering agents have been found to be effective for PBC.The aim of this study was to examine the safety and efficacy of fenofibrate, a member of the fibrate class of hypolipidemic and anti-inflammatory agent via peroxysome proliferatory-activated receptor α,in patients with aPBC.METHODS:Fenofibrate was administered for twelve weeks in nine patients with aPBC who failed to respond to UDCA.UDCA was used along with fenofibrate during the study.The data from aPBC patients were analyzed to assess the biochemical effect of fenofibrate during the study.RESULTS: The serum levels of alkaline phosphatase (ALP)(285±114.8IU/L) and immunoglobulin M (IgM) (255.8±85.9mg/dl) significantly decreased to 186.9±76.2IU/L and 192.9±67.5mg/dL respectively, after fenofibrate treatment in patients with aPBC (P<0.05). Moreover,the titer of antimitochondrial antibody (AMA) also decreased in 4 of 9 patients with aPBC. No adverse reactions were observed in any patients.CONCLUSION:Fenofibrate appears to be significantly effective in treating patients with aPBC who respond incompletely to UDCA alone.Although the mechanism of fenofibrate on aPBC has not yet been fully clarified,combination therapy using fenofibrate and UDCA might be related to the anti-immunological effects, such as the suppression of AMA production as well as its antiinflammatory effect.
文摘Increasing population density and development of mountainous terrain have brought human settlements within reach of landslide hazards.In recent years,due to the shortening of return period for severe natural events such as heavy rainfall,snowline retreating,great earthquake together with human activities,catastrophic landslides happened more frequently than before,resulting in large-scale casualties due to the increasing occurrences of rapid long-runout rock avalanches,especially in China.This paper presents some typical case histories related to the catastrophic landslides,including the Guanling rock avalanche,the Yigong rockslide-debris avalanche,the Wenchuan earthquake-induced landslides and the Danba landslide.They occurred in the last decade.Moreover,taking the Jiweishan catastrophic rockslide-fragment flow and the Yuhuangge landslide located in the new Wushan Town for examples,early-warning system and risk management on landslides are discussed in detail.
基金National Natural Science Foundation of China No.40101028+2 种基金 Knowledge Innovation Project of the Geographic Sciences and Natural Resources Research CAS No.CXIOG-D02-02
文摘Both marginal fluctuation and areal change were used to detect the accurate dynamics of glacier change in the study area using Landsat MSS, ETM, SPOT HRV and topographic maps based on GIS. From 1963 to 1977, four of eight glaciers advanced, two of them retreated and another two kept stable, the glacier advanced generally. From 1977 to 1986, four of eight glaciers retreated and the others kept stable, but the retreated glaciers were those which advanced from 1963 to 1977. From 1986 to 2000, seven of eight glaciers retreated and only one glacier kept stable, the retreating velocity was 10-15 m/a. Glacier recession in this period became very fast and universal. From 1963 to 2000, the area of glaciers decreased from 5479.0 ha to 4795.4 ha, up to 12.5%. It is alarming that most of glacier retreats happened from 1986 to 2000. This was very consistent with change process of summer mean temperature in this region and global warming beginning in the 1980s.
基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19070501)the National Natural Science Foundation of China(41730751&41671066)the International Partnership Program of Chinese Academy of Sciences(131C 11KYSB20160061,Y560L01001).
文摘Global warming triggers shrinking and thinning of glaciers worldwide,with potentially severe implications for human society.However,regional differences in glacier retreat and its relationship with climatic characteristics have not been conclusively demonstrated.In this study,regional changes in global glaciers based on two primary features,area change and mass balance,were investigated on the basis of data collected from published research on glacier changes.Results show that during the period 1980—2015,the rate of global glacier area shrinkage was 0.18%per year and that of global glacier mass loss was 0.25 m w.e.per year.Retreat of glaciers located at low and middle latitudes was characterized by severe area shrinkage and mass loss.Correspondingly,in the Arctic,deglaciation was characterized by ice thinning due to a low area reduction but relatively high mass loss rate.However,glaciers in high southern latitudes were in a relatively stable status.High Mountain Asia exhibited the lowest rate of area shrinkage and mass loss among glaciers located at low and middle latitudes,and a slower rate of mass loss compared with the global average.Glaciers in the Tropical Andes exhibited the fastest rate of glacier area shrinkage(—1.6%per year),whereas Antarctic and Subantarctic glaciers showed the lowest rate(—0.11%per year).For mass balance,the most negative occurred at Southern Andes(—0.81 m w.e.per year),followed by Alaska(-0.74 m w.e.per year).Only the Antarctic and Subantarctic experienced small mass gain(0.04 m w.e.per year).High levels of correlation are found between the rates of glacier retreat and annual average temperature and annual total precipitation instead of their trends.The variability of the surface climate conditions in the glacier environment plays a key role in driving these regional differences in global glacier retreat.
基金Funding was provided by Global Change Research Program of China (No. 2015CB953900)the Key Project of the National Natural Science Foundation of China (No. 41330960)
文摘Arctic sea ice has significant seasonal variability. Prior to the 2000 s, it retreated about 15% in summer and fully recovered in winter. However, by the year 2007, Arctic sea ice extent experienced a catastrophic decline to about 4.28×10^6 km^2, which was 50% lower than conditions in the 1950 s to the 1970 s(Serreze et al., 2008). That was a record low over the course of the modern satellite record, since 1979(note that the year 2012 became the new record low). This astonishing event drew wide-ranging attention in 2007-2009 during the 4 th International Polar Year. The dramatic decline of sea ice attracts many scientists’ interest and has become the focus of intense research since then. Currently, sea ice retreat is not only appearing around the marginal ice zone, but also in the pack ice inside the central Arctic(Zhao et al., 2018). In fact, premonitory signs had already been seen through other evidence. Before the disintegration of the Soviet Union, US naval submarines had been conducting an extensive survey under the sea ice and taking measurements of sea ice thickness. Their measurements revealed a gradual decrease of ice thickness to 1.8 m during winter by the end of the 20 th century, in contrast to the climatological mean of 3.1 m(Rothrock et al., 1999). However, this alarming result did not draw much attention since the Arctic was still severely cold at that time.
基金National Key Basic Research and Development Planning Program of China(Program 973)(2013CB430202)Basic Research Program of Jiangsu Province,China(BK20130997)+1 种基金National Natural Science Fund of China(91337109)Project Funded by the Priority Academic program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.
基金financially supported by the National Basic Research Program of China(2015CB954101)the National Science and Technology Basic Special Project(2011FY11040-2)+1 种基金the National Natural Science Foundation of China(41171332,41571388)the Surveying and Mapping Geoinformation Nonprofit Specific Project(201512033)
文摘Inland lakes and alpine glaciers are important constituents of water resources in arid and semiarid regions. Understanding their variations is critical for both an accurate evaluation of the dynamic changes of water resources and the retrieval of climatic information. On the basis of earlier researches, this study investigated the growth of the Sayram Lake and the retreat of its water-supplying glaciers in the Tianshan Mountains using long-term sequenced remote sensing images. Our results show that over the past 40 years, the surface area and the water level of the lake has increased by 12.0±0.3 km<sup>2</sup> and 2.8 m, respectively, and the area of its water-supplying glaciers has decreased continuously since the early 1970s with a total reduction of about–2.13±0.03 km<sup>2</sup>. Our study has indicative significance to the research of regional climate change.
文摘The glacier on the Yulong Mountain is one of the most important attractions in Lijiang, Yunnan, China. But it keeps retreating these years due to global warming, which is bound to influence regional tourism significantly in Lijiang. This study estimates the effects of the glacier retreat of the Yulong Mountains on tourism there. Primary data were collected through a visitor survey including demographics, motives, lengths of stay, and opinions about each tourism resource from tourists to Lijiang, as well as questions about which scenic spot(s) they had visited or would visit, how much they expended per day during their visit and how their visiting behavior would be changed upon the hypothesis that the glacier would disappear. These data were used to analyze the proportion of the contribution of glacier to the tourism in Lijiang and estimate the impact of glacier on the regional tourism quantitatively. According to the survey, it could be concluded that three quarters of the tourists to Lijiang were interested in the Yulong Mountain glacier, indicating that the glacier possesses notable appeal for sightseeing tourists. The results of our analysis showed that about 689,013-1,508,247 tourists, accounting for 19.63-42.97 % of the total 3,510,000 domestic tourists to Lijiang in 2004, would not come to Lijiang in the absence of the glacier, resulting in a possible direct economic loss of 84,382,508-184,713,011 USD (viz. 700,374,824-1,533,117,993 RMB) and a markedly decrease in the attraction radius.
文摘For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines.Studies showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000 s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local stability.Global stability is addressed primarily through proper pillar design, and became a major focus after the2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:(1) leaving an engineered final stump, rather than extracting the entire pillar,(2) enhancing roof bolt support, particularly in intersections, and(3) increasing the use of mobile roof supports(MRS). A final component was an emphasis on better management of pillar recovery operations.This included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations,and hazard identification. As retreat mines have incorporated these elements into their roof control plans,it has become clear that pillar recovery is not ‘‘inherently unsafe." The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.
文摘The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.
文摘Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered7 To help answer these questions, and to determine some of the relevant factors influencing the conditions of room and pillar (R & P) retreat min- ing entries, four consecutive R & P retreat panels were evaluated. This evaluation was intended to rein- force the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry. This paper details observations were made in four consecutive R & P retreat panels and the data were collected from an instrumentation site during retreat mining. The pri- mary focus was on the differences observed among the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the obse^ation and |ll^trumentation, numerical modeling was per- formed to evaluate the stress condi~!ons. Both the LaModel 3.0 and Rocscience Phase 2 programs were used to evaluate these four panels, The results of both models indicated a drastic reduction in the vertical stresses experienced in these panels due to the full extraction mining in overlying seams when compared to the full overburden load. Both models showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. These efforts provided two overarching conclusions concerning R & P retreat mine planning and execution. The first was that there are four areas that should not be overlooked during R & P retreat mining: topographic relief, multiple^seaPa stress relief, stress concentrations near the gob edge, and geologic changes in the immediate roof. The second is that in order to successfully retreat an R & P panel, a three-phased approach to the design and analysis of the panel should be conducted: the planning phase, evaluation phase, and monitoring phase.
基金Project(2014QNA50) supported by Fundamental Research Funds for the Central Universities,ChinaProject(51404248) supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD) of Jiangsu Higher Education Institutions,China
文摘The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.
基金supported by the National Science Foundation of China (No.40976057)the State Oceanic Administration of China (No.908-02-03-04)
文摘Based on the field surveys and repeated cross-profile observations combined with the comparison of many years’ topog-raphic maps,this study shows the spatial variability and varying patterns of coastal erosion along the west coast of the Taiwan Strait.Regional differentiation in the Meso-Cenozoic coastal tectonics determined the irregular coastline and geological background for large-scale coastal erosion distribution.The intensity of coastal erosion on the west side of the Taiwan Strait is mild in the northern region,severe in the central region and modest in the southern region.The beaches along the coast are mainly backed by dunes,sea-walls or cliffs.The dunes and beaches show periodic erosion and recovery along the coast adjacent to river mouths,while persistent retreat of frontal dunes and beaches tends to occur in other areas.The beach erosion occurs mainly in front of seawalls.Due to the low strength of the unconsolidated sediment the soft cliffs suffer the severest coastline recession.Sea level rise and river sediment discharge reduction are main causes of coastal erosion.Storm surge is common in the studied area and plays an important role in the progress of coastal erosion.Human activities including coastal constructions and sand mining also tend to interfere strongly with the balance of sediment budget in some coastal cells.
基金supported by the National Natural Science Foundation of China(90302006,40371026,90511007,40501014)G REEI of the Chinese Academy of Sciences(2004102)+1 种基金the Hundred Talents Program(2004401,KZCX3-SW-339)of the Chinese Academy of Sciencesthe Project for Outstanding Scientists(40121101)of the National Natural Science Foundation.
文摘As the unprecedented global warming is under way, the glacier retreat is getting more and more serious. In the inland arid area of Northwest China, due to very scarce precipitation, where there is water, there are oases. And the glacier melt water amounts to 22 % of the total direct supply of the inland river water and is of crucial importance to the survival and development of the oases. In this paper, using both the observed data and the previous research achievements of the glaciers in the inland valley of Northwest China where the oasis depending on the glacier is the only location suitable for human living, the authors describe the glacier retreat trend over the past half century, focusing on discussing the possible impact of the glacier retreat on the melt water runoff that is almost the only water resource efficient to nourish the oases. The authors find that even with increasing amount of water from the glacier with global warming, the water shortage is getting more and more serious and the environment is under a degrading way due to the accelerating economical development. The water shortage is bound to be more serious if the glacier retreat keeps on, especially after the glacier melt water is over its top for the degradedglacier scale. So suggestions are stressed in the end that a new water-saving pattern should be adopted in the area for a sustainable development due to the warming-up induced continuous glacier retreat.
基金funded by the National Natural Science Foundation of China(Grant Nos.41907396,42001388,42071277)Chongqing Research Program of Basic Research and Frontier Technology(No.cstc2019jcyj-msxmX0515)+3 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202200526)Preferential Funding Scheme for Ideological and Political Teachers and Counselors in Colleges and Universities(Grant No.FDYZY2020003)the Science Foundation of the Chongqing Normal University(22XLB002,22XLB003)Humanities and Social Sciences Research Program of Chongqing Education Commission(22SKSZ030)。
文摘The Chenab basin is located in northwest India and eastern Pakistan.Glaciers in Chenab basin,as local freshwater resources,are very important to the regional ecological environment and development.At the same time,SBAS InSAR can monitor the deformation of the ground for a long time,the monitoring accuracy can reach mm level,and can obtain the time series change of deformation,whcih provides a new idea and method for glacier detection.In this study,the deformation from SBAS InSAR was combined with glacial area data to study the glacial changes in Chenab Basin.Sentinel-1 and Landsat series images were used to obtain the deformation and change in the area of glaciers by SBAS InSAR and the semi-automated method.The results showed that glaciers in the Chenab basin retreated rapidly,especially in the past ten years.The glacier area decreased by 88.05 km^(2)in 1990~2000 and 118.86 km^(2) in 2000~2010,and the glacier area decreased by 236.01 km^(2) in 2010~2020,which was the largest rate of change of 9.49%.Moreover,glacial deformation decreased in 2020,and the deformation rate ranged from-146.3mm/a to 119.52 mm/a.Most glaciers had deformation rates between-50 mm/a and 50 mm/a.Influenced by precipitation and temperature,glacial deformation in the Chenab basin started to change in August,the maximum accumulation was 6,828.43mm,and the minimum ablation was-20,656.41 mm.