Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored...Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored.In this study,we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space.By comparing the results of the two models,we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves.Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space.Specifically,the dynamic stress concentration factor(DSCF)of the lining in the elastic half-space exhibits periodic fluctuations,influenced by the incident wave frequency and tunnel depth,while the DSCF in the infinitely elastic space remain stable.Overall,the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves.Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.展开更多
Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface r...Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.展开更多
Surface albedo is a quantitative indicator for land surface processes and climate modeling,and plays an important role in surface radiation balance and climate change.In this study,by means of the MCD43A3 surface albe...Surface albedo is a quantitative indicator for land surface processes and climate modeling,and plays an important role in surface radiation balance and climate change.In this study,by means of the MCD43A3 surface albedo product developed on the basis of Moderate Resolution Imaging Spectroradiometer(MODIS),we analyzed the spatiotemporal variation,persistence status,land cover type differences,and annual and seasonal differences of surface albedo,as well as the relationship between surface albedo and various influencing factors(including Normalized Difference Snow Index(NDSI),precipitation,Normalized Difference Vegetation Index(NDVI),land surface temperature,soil moisture,air temperature,and digital elevation model(DEM))in the north of Xinjiang Uygur Autonomous Region(northern Xinjiang)of Northwest China from 2010 to 2020 based on the unary linear regression,Hurst index,and Pearson's correlation coefficient analyses.Combined with the random forest(RF)model and geographical detector(Geodetector),the importance of the above-mentioned influencing factors as well as their interactions on surface albedo were quantitatively evaluated.The results showed that the seasonal average surface albedo in northern Xinjiang was the highest in winter and the lowest in summer.The annual average surface albedo from 2010 to 2020 was high in the west and north and low in the east and south,showing a weak decreasing trend and a small and stable overall variation.Land cover types had a significant impact on the variation of surface albedo.The annual average surface albedo in most regions of northern Xinjiang was positively correlated with NDSI and precipitation,and negatively correlated with NDVI,land surface temperature,soil moisture,and air temperature.In addition,the correlations between surface albedo and various influencing factors showed significant differences for different land cover types and in different seasons.To be specific,NDSI had the largest influence on surface albedo,followed by precipitation,land surface temperature,and soil moisture;whereas NDVI,air temperature,and DEM showed relatively weak influences.However,the interactions of any two influencing factors on surface albedo were enhanced,especially the interaction of air temperature and DEM.NDVI showed a nonlinear enhancement of influence on surface albedo when interacted with land surface temperature or precipitation,with an explanatory power greater than 92.00%.This study has a guiding significance in correctly understanding the land-atmosphere interactions in northern Xinjiang and improving the regional land-surface process simulation and climate prediction.展开更多
We present the best bounds on the distance between 3-direction quartic box spline surface patch and its control net by means of analysis and computing for the basis functions of 3-direction quartic box spline surface....We present the best bounds on the distance between 3-direction quartic box spline surface patch and its control net by means of analysis and computing for the basis functions of 3-direction quartic box spline surface.Both the local bounds and the global bounds are given by the maximum norm of the first differences or second differences or mixed differences of the control points of the surface patch.展开更多
In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been...In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been considered to reduce these effects in technical literature.The present study aims to investigate the role of geofoam as the cover material in cut and cover tunnels on the seismic response of the ground surface.For this purpose,a numerical study was performed using FLAC 2D,a finite difference software,and verified against previous studies.The effects of parameters such as the geofoam type,thickness of the geofoam blocks and interfaces between the blocks,on the ground surface amplification pattern were investigated.Parametric studies demonstrate that the geofoam has a strong potential to attenuate the seismic horizontal movements of the ground surface.As the thickness of the geofoam blocks is decreased,its attenuation ability is increased.It was also determined that the interface between the geofoam blocks plays a key role in the attenuation of the aboveground seismic responses.Based on the results,it was concluded that geofoam is a proper material to attenuate seismic amplifications at the ground surface,induced by underground tunnels.展开更多
An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12^th, 2008 and resulted in long surface ruptures (〉300 km). The first-hand observations about the surface ruptures produced by the earth...An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12^th, 2008 and resulted in long surface ruptures (〉300 km). The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu, Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt. Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beiehuan rupture zone reach 2.514 m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m. The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component. The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents.展开更多
Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Car...Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.展开更多
The Garzê–Yushu strike-slip fault in central Tibet is the locus of strong earthquakes(M 〉 7). The deformation and geometry of the co-seismic surface ruptures are reflected in the surface morphology of the fau...The Garzê–Yushu strike-slip fault in central Tibet is the locus of strong earthquakes(M 〉 7). The deformation and geometry of the co-seismic surface ruptures are reflected in the surface morphology of the fault and depend on the structure of the upper crust as well as the pre-existing tectonics. Therefore, the most recent co-seismic surface ruptures along the Garzê–Yushu fault zone(Dangjiang segment) reveal the surface deformation of the central Tibetan Plateau. Remote sensing images and field investigations suggest a 85 km long surface rupture zone(striking NW-NWW), less than 50 m wide, defined by discontinuous fault scarps, right-stepping en echelon tensional cracks and left-stepping mole tracks that point to a left-lateral strike-slip fault. The gullies that cross fault scarps record systematic left-lateral offsets of 1.8 m to 5.0 m owing to the most recent earthquake, with moment magnitude of about M 7.5, in the Dangjiang segment. Geological and geomorphological features suggest that the spatial distribution of the 1738 co-seismic surface rupture zone was controlled by the pre-existing active Garzê–Yushu fault zone(Dangjiang segment). We confirm that the Garzê–Yushu fault zone, a boundary between the Bayan Har Block to the north and the Qiangtang Block to the south, accommodates the eastward extrusion of the Tibetan Plateau and generates strong earthquakes that release the strain energy owing to the relative motion between the Bayan Har and Qiangtang Blocks.展开更多
The relationship between the factor of temperature difference of the near-surface layer(T_(1000 hPa)-T_(2m))and sea fog is analyzed using the NCEP reanalysis with a horizontal resolution of l°xl°(2000 to 201...The relationship between the factor of temperature difference of the near-surface layer(T_(1000 hPa)-T_(2m))and sea fog is analyzed using the NCEP reanalysis with a horizontal resolution of l°xl°(2000 to 2011) and the station observations(2010 to 2011).The element is treated as the prediction variable factor in the GRAPES model and used to improve the regional prediction of sea fog on Guangdong coastland.(1) The relationship between this factor and the occurrence of sea fog is explicit:When the sea fog happens,the value of this factor is always large in some specific periods,and the negative value of this factor decreases significantly or turns positive,suggesting the enhancement of warm and moist advection of air flow near the surface,which favors the development of sea fog.(2) The transportation of warm and moist advection over Guangdong coastland is featured by some stages and the jumping among these states.It also gets stronger over time.Meanwhile,the northward propagation of warm and moist advection is quite consistent with the northward advancing of sea fog from south to north along the coastland of China.(3) The GRAPES model can well simulate and realize the factor of near-surface temperature difference.Besides,the accuracy of regional prediction of marine fog,the relevant threat score and Heidke skill score are all improved when the factor is involved.展开更多
In this paper,we derived the relationships between the travel time difference of sPn and Pn and the local earthquake focal depth.In these equations,the travel time difference of sPn and Pn is not related to the epicen...In this paper,we derived the relationships between the travel time difference of sPn and Pn and the local earthquake focal depth.In these equations,the travel time difference of sPn and Pn is not related to the epicentral distance,but depends only on the regional crustal mode and the focal depth.According to the equations,we provided a simple and accurate method to determine local earthquake focal depth by using the travel time difference between phase sPn and Pn.This method has been used to determine the focal depths of two earthquake of MS6.1 and MS5.6 which occurred at the junction of Panzhihua and Huili,Sichuan on August 30 and 31,2008.The results were compared to those from other sources such as the China Earthquake Networks Center,and the comparison shows that the results are accurate and reliable.展开更多
The northeastern part of the Tibetan Plateau is a region where different tectonic blocks collide and intersect,and large earthquakes are frequent.Global Navigation Satellite System(GNSS)observations show that tectonic...The northeastern part of the Tibetan Plateau is a region where different tectonic blocks collide and intersect,and large earthquakes are frequent.Global Navigation Satellite System(GNSS)observations show that tectonic deformation in this region is strong and manifests as non-uniform deformation associated with tectonic features.S-wave splitting studies of near-field seismic data show that seismic anisotropy parameters can also reveal the upper crustal medium deformation beneath the reporting station.In this paper,we summarize the surface deformation from GNSS observations and crustal deformation from seismic anisotropy data in the northeastern Tibetan Plateau.By comparing the principal compressive strain direction with the fast S-wave polarization direction of near-field S-wave splitting,we analyzed deformation and its differences in surface and upper crustal media in the northeastern Tibetan Plateau and adjacent areas.The principal compressive strain direction derived from GNSS is generally consistent with the polarization direction of fast S-waves,but there are also local tectonic regions with large differences between them,which reflect the different deformation mechanisms of regional upper crustal media.The combination of GNSS and seismic anisotropy data can reveal the depth variation characteristics of crustal deformation and deepen understanding of three-dimensional crustal deformation and the deep dynamical mechanisms underlying it.it.展开更多
Long-term variations in a sea surface wind speed (WS) and a significant wave height (SWH) are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource ex...Long-term variations in a sea surface wind speed (WS) and a significant wave height (SWH) are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource exploitation, and other activities. The seasonal characteristics of the long-term trends in China's seas WS and SWH are determined based on 24 a (1988-2011) cross-calibrated, multi-platform (CCMP) wind data and 24 a hindcast wave data obtained with the WAVEWATCH-III (WW3) wave model forced by CCMP wind data. The results show the following. (1) For the past 24 a, the China's WS and SWH exhibit a significant increasing trend as a whole, of 3.38 cm/(s.a) in the WS, 1.3 cm/a in the SWH. (2) As a whole, the increasing trend of the China's seas WS and SWH is strongest in March-April-May (MAM) and December-January-February (DJF), followed by June-July-August (JJA), and smallest in September-October-November (SON). (3) The areal extent of significant increases in the WS was largest in MAM, while the area decreased in JJA and DJF; the smallest area was apparent in SON. In contrast to the WS, almost all of China's seas exhibited a significant increase in SWH in MAM and DJF; the range was slightly smaller in JJA and SON. The WS and SWH in the Bohai Sea, the Yellow Sea, East China Sea, the Tsushima Strait, the Taiwan Strait, the northern South China Sea, the Beibu Gull and the Gulf of Thailand exhibited a significant increase in all seasons. (4) The variations in China's seas SWH and WS depended on the season. The areas with a strong increase usually appeared in DJF.展开更多
This paper presents the integration of seismic refraction and multichannel analysis of surface wave(MASW)measurements to investigate the anisotropy of P-and S-wave velocities.Additionally,synthetic forward modelling i...This paper presents the integration of seismic refraction and multichannel analysis of surface wave(MASW)measurements to investigate the anisotropy of P-and S-wave velocities.Additionally,synthetic forward modelling is presented as a tool for supporting seismic anisotropy studies.The geophysical measurements of cracks allowed to recognise the fracturing of a granite rock mass in a Paleozoic granite quarry(Strzegom,Poland)and a dolomite rock mass in a Triassic dolomite quarry(Podlesna,Poland).Application of the forward modelling supports the interpretation of seismic methods,simplifying data processing and verifying the final results based on data from difficult seismic conditions.As a result of direct measurements,two crack systems were determined in granite rock mass:NNE-SSW and NNW-SSE,and two in dolomite rock mass:NNE-SSW and NW-SE.Furthermore,the numerical results show the relationship between the highest values of P-and S-wave velocities and separated crack systems which allowed an unequivocal interpretation of the direction of stress,resulting in the deformations.The obtained information is promising to be helpful in mining exploration for optimising excavation works.展开更多
The"5.12"Wenchuan earthquake in 2008 triggered a large number of co-seismic landslides.The rear boundary or cracks of co-seismic landslide are generally located at the steep free surface of thin or thick mou...The"5.12"Wenchuan earthquake in 2008 triggered a large number of co-seismic landslides.The rear boundary or cracks of co-seismic landslide are generally located at the steep free surface of thin or thick mountains.Dynamic process of this kind of landslides could be divided into two parts:the seismic dynamic response of the slope and the movement process of rock mass.Taking the Laoyingyan rockslide as an example,the amplification effect was studied by single-degree-of-freedom system analysis method.Besides,the dynamic process of landslide under seismic loading was simulated by the finite difference method(FDM)and discrete element method(DEM).The amplification coefficient of the rockslide to seismic wave is 1.25.The results show that the critical sliding surface of the Laoyingyan rockslide was formed at the 23 th seconds under the action of seismic wave.At the same time,tension failure occurred at the rear edge of the sliding mass and shear failure occurred at the front edge.The maximum displacement was 0.81 m and the initial velocity was 2.78 m/s.During the initiation process of the rockslide,the rock mass firstly broke down along the joints which are along the dip of the rock stratum,and then collapsed bodily along the secondary structural planes.In the process of movement,the maximum velocity of rock mass was 38.24 m/s.After that,the rock mass underwent multiple collisions,including contact,deceleration to 0 and speed recovery after rebound.Finally,due to the constant loss of energy,the rocks stopped and accumulated loosely at the foot of the slope.The longest distance of movement was about 494 m.Besides,the smaller the damping ratio,the farther the rock mass moved.Compared with the results without considering the amplification factor,the movement distance of landslide by considering the amplification factor was more accurate.The study of the Laoyingyan rockslide is helpful to strengthen our field identification of potential co-seismic rockslides.At the same time,understanding its movement and accumulation process can help us better predict the hazard scope of the co-seismic rockslides,and provide a reference for the design of treatment projects.展开更多
This study employs Landsat-8 Operational Land Imager (OLI) thermal infrared satellite data to compare land surface temperature of two cities in Ghana: Accra and Kumasi. These cities have human populations above 2 mill...This study employs Landsat-8 Operational Land Imager (OLI) thermal infrared satellite data to compare land surface temperature of two cities in Ghana: Accra and Kumasi. These cities have human populations above 2 million and the corresponding anthropogenic impact on their environments significantly. Images were acquired with minimum cloud cover (<10%) from both dry and rainy seasons between December to August. Image preprocessing and rectification using ArcGIS 10.8 software w<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ere</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> used. The shapefiles of Accra and Kumasi were used to extract from the full scenes to subset the study area. Thermal band data numbers were converted to Top of Atmospheric Spectral Radiance using radiance rescaling factors. To determine the density of green on a patch of land, normalized difference vegetation index (NDVI) was calculated by using red and near-infrared bands </span><i><span style="font-family:Verdana;">i.e</span></i></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> Band 4 and Band 5. Land surface emissivity (LSE) was also calculated to determine the efficiency of transmitting thermal energy across the surface into the atmosphere. Results of the study show variation of temperatures between different locations in two urban areas. The study found Accra to have experienced higher and lower dry season and wet season temperatures, respectively. The temperature ranges corresponding to the dry and wet seasons were found to be 21.0985</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 46.1314</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;">, and, 18.3437</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 30.9693</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> respectively. Results of Kumasi also show a higher range of temperatures from 32.6986</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 19.1077<span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> during the dry season. In the wet season, temperatures ranged from 26.4142</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">-</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">0</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.898728</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;">. Among the reasons for the cities of Accra and Kumasi recorded higher than corresponding rural areas’ values can be attributed to the urban heat islands’ phenomenon.</span></span></span></span>展开更多
The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the sprin...The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.展开更多
As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scal...As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete(RC)frame structure.Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance.Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions.A seismic fragility study of displacement demand is conducted based on numerical simulation.The acceleration response and displacement response of different combinations are compared.The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.展开更多
Composite electromagnetic scattering from a two-dimensional (2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain (FDTD) method. A uniaxial perfectly mat...Composite electromagnetic scattering from a two-dimensional (2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain (FDTD) method. A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices.The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly. To validate the proposed numerical technique,a 2D infinitely long cylinder over the sea surface is taken into account first.The variation of angular distribution of the scattering changing with incident angle is calculated. The results show good agreement with the conventional moment method. Finally,the influence of the incident angle,the polarization,and the size of the ship-like target on the composite scattering coefficient is discussed in detail.展开更多
基金supported by the National Natural Science Foundation of China[grant number 51991393]support from the Guangdong Provincial Key Laboratory of Earthquake Engineering and Applied Technology and Key Laboratory of Earthquake Resistance,Earthquake Mitigation,and Structural Safety funded by the Ministry of Education。
文摘Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored.In this study,we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space.By comparing the results of the two models,we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves.Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space.Specifically,the dynamic stress concentration factor(DSCF)of the lining in the elastic half-space exhibits periodic fluctuations,influenced by the incident wave frequency and tunnel depth,while the DSCF in the infinitely elastic space remain stable.Overall,the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves.Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.
基金funded by the Basic Research Program of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant Nos.CEAIEF20220102,2021IEF0505,and CEAIEF2022050502)the National Natural Science Foundation of China(Grant Nos.42072248 and 42041006)the National Key Research and Development Program of China(Grant Nos.2021YFC3000601-3 and 2019YFE0108900)。
文摘Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.
基金This research was supported by the National Key Research and Development Program of China(2019YFC1510505)the Xinjiang University PhD Start-up Fund(BS210226)the National College Student Research Training Plan of China(202210755004).
文摘Surface albedo is a quantitative indicator for land surface processes and climate modeling,and plays an important role in surface radiation balance and climate change.In this study,by means of the MCD43A3 surface albedo product developed on the basis of Moderate Resolution Imaging Spectroradiometer(MODIS),we analyzed the spatiotemporal variation,persistence status,land cover type differences,and annual and seasonal differences of surface albedo,as well as the relationship between surface albedo and various influencing factors(including Normalized Difference Snow Index(NDSI),precipitation,Normalized Difference Vegetation Index(NDVI),land surface temperature,soil moisture,air temperature,and digital elevation model(DEM))in the north of Xinjiang Uygur Autonomous Region(northern Xinjiang)of Northwest China from 2010 to 2020 based on the unary linear regression,Hurst index,and Pearson's correlation coefficient analyses.Combined with the random forest(RF)model and geographical detector(Geodetector),the importance of the above-mentioned influencing factors as well as their interactions on surface albedo were quantitatively evaluated.The results showed that the seasonal average surface albedo in northern Xinjiang was the highest in winter and the lowest in summer.The annual average surface albedo from 2010 to 2020 was high in the west and north and low in the east and south,showing a weak decreasing trend and a small and stable overall variation.Land cover types had a significant impact on the variation of surface albedo.The annual average surface albedo in most regions of northern Xinjiang was positively correlated with NDSI and precipitation,and negatively correlated with NDVI,land surface temperature,soil moisture,and air temperature.In addition,the correlations between surface albedo and various influencing factors showed significant differences for different land cover types and in different seasons.To be specific,NDSI had the largest influence on surface albedo,followed by precipitation,land surface temperature,and soil moisture;whereas NDVI,air temperature,and DEM showed relatively weak influences.However,the interactions of any two influencing factors on surface albedo were enhanced,especially the interaction of air temperature and DEM.NDVI showed a nonlinear enhancement of influence on surface albedo when interacted with land surface temperature or precipitation,with an explanatory power greater than 92.00%.This study has a guiding significance in correctly understanding the land-atmosphere interactions in northern Xinjiang and improving the regional land-surface process simulation and climate prediction.
基金Supported by the National Natural Science Foundation of China (61170324 and 61100105)
文摘We present the best bounds on the distance between 3-direction quartic box spline surface patch and its control net by means of analysis and computing for the basis functions of 3-direction quartic box spline surface.Both the local bounds and the global bounds are given by the maximum norm of the first differences or second differences or mixed differences of the control points of the surface patch.
文摘In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been considered to reduce these effects in technical literature.The present study aims to investigate the role of geofoam as the cover material in cut and cover tunnels on the seismic response of the ground surface.For this purpose,a numerical study was performed using FLAC 2D,a finite difference software,and verified against previous studies.The effects of parameters such as the geofoam type,thickness of the geofoam blocks and interfaces between the blocks,on the ground surface amplification pattern were investigated.Parametric studies demonstrate that the geofoam has a strong potential to attenuate the seismic horizontal movements of the ground surface.As the thickness of the geofoam blocks is decreased,its attenuation ability is increased.It was also determined that the interface between the geofoam blocks plays a key role in the attenuation of the aboveground seismic responses.Based on the results,it was concluded that geofoam is a proper material to attenuate seismic amplifications at the ground surface,induced by underground tunnels.
文摘An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12^th, 2008 and resulted in long surface ruptures (〉300 km). The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu, Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt. Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beiehuan rupture zone reach 2.514 m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m. The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component. The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents.
基金supported by the National Natural Science Foundation of China(Grant Nos.61308071,61601355,and 61571355)the Natural Science Foundation of Shaanxi Province,China(Grant No.2016JM6011)
文摘Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.
基金supported by the China Earthquake Administration Research Fund(Grant No.DZJ2016-18)the National Natural Science Foundation of China(Grant No.41602222)
文摘The Garzê–Yushu strike-slip fault in central Tibet is the locus of strong earthquakes(M 〉 7). The deformation and geometry of the co-seismic surface ruptures are reflected in the surface morphology of the fault and depend on the structure of the upper crust as well as the pre-existing tectonics. Therefore, the most recent co-seismic surface ruptures along the Garzê–Yushu fault zone(Dangjiang segment) reveal the surface deformation of the central Tibetan Plateau. Remote sensing images and field investigations suggest a 85 km long surface rupture zone(striking NW-NWW), less than 50 m wide, defined by discontinuous fault scarps, right-stepping en echelon tensional cracks and left-stepping mole tracks that point to a left-lateral strike-slip fault. The gullies that cross fault scarps record systematic left-lateral offsets of 1.8 m to 5.0 m owing to the most recent earthquake, with moment magnitude of about M 7.5, in the Dangjiang segment. Geological and geomorphological features suggest that the spatial distribution of the 1738 co-seismic surface rupture zone was controlled by the pre-existing active Garzê–Yushu fault zone(Dangjiang segment). We confirm that the Garzê–Yushu fault zone, a boundary between the Bayan Har Block to the north and the Qiangtang Block to the south, accommodates the eastward extrusion of the Tibetan Plateau and generates strong earthquakes that release the strain energy owing to the relative motion between the Bayan Har and Qiangtang Blocks.
基金Chinese Special Scientific Research Project for Public Interest(GYHY200906008)Natural Science Foundation of China(41275025)+2 种基金Guangdong Science and Technology Plan Project(2012A061400012)Meteorological Project from Guangdong Meteorological Bureau(201003)Research on Pre-warning and Forecasting Techniques for Marine Meteorology from Guangdong Meteorological Bureau
文摘The relationship between the factor of temperature difference of the near-surface layer(T_(1000 hPa)-T_(2m))and sea fog is analyzed using the NCEP reanalysis with a horizontal resolution of l°xl°(2000 to 2011) and the station observations(2010 to 2011).The element is treated as the prediction variable factor in the GRAPES model and used to improve the regional prediction of sea fog on Guangdong coastland.(1) The relationship between this factor and the occurrence of sea fog is explicit:When the sea fog happens,the value of this factor is always large in some specific periods,and the negative value of this factor decreases significantly or turns positive,suggesting the enhancement of warm and moist advection of air flow near the surface,which favors the development of sea fog.(2) The transportation of warm and moist advection over Guangdong coastland is featured by some stages and the jumping among these states.It also gets stronger over time.Meanwhile,the northward propagation of warm and moist advection is quite consistent with the northward advancing of sea fog from south to north along the coastland of China.(3) The GRAPES model can well simulate and realize the factor of near-surface temperature difference.Besides,the accuracy of regional prediction of marine fog,the relevant threat score and Heidke skill score are all improved when the factor is involved.
基金funded by the special support projectentitled "Sorting out and processing of seismic data " of central public-interest basic scientific and technological research of Institute of Crustal DynamicsChina Earthquake Administration (ZDJ2007-4)
文摘In this paper,we derived the relationships between the travel time difference of sPn and Pn and the local earthquake focal depth.In these equations,the travel time difference of sPn and Pn is not related to the epicentral distance,but depends only on the regional crustal mode and the focal depth.According to the equations,we provided a simple and accurate method to determine local earthquake focal depth by using the travel time difference between phase sPn and Pn.This method has been used to determine the focal depths of two earthquake of MS6.1 and MS5.6 which occurred at the junction of Panzhihua and Huili,Sichuan on August 30 and 31,2008.The results were compared to those from other sources such as the China Earthquake Networks Center,and the comparison shows that the results are accurate and reliable.
基金supported by the National Natural Science Foundation of China(No.42074065)the basic research project of Institute of Earthquake Forecasting China Earthquake Administration(No.2021IEF0601)。
文摘The northeastern part of the Tibetan Plateau is a region where different tectonic blocks collide and intersect,and large earthquakes are frequent.Global Navigation Satellite System(GNSS)observations show that tectonic deformation in this region is strong and manifests as non-uniform deformation associated with tectonic features.S-wave splitting studies of near-field seismic data show that seismic anisotropy parameters can also reveal the upper crustal medium deformation beneath the reporting station.In this paper,we summarize the surface deformation from GNSS observations and crustal deformation from seismic anisotropy data in the northeastern Tibetan Plateau.By comparing the principal compressive strain direction with the fast S-wave polarization direction of near-field S-wave splitting,we analyzed deformation and its differences in surface and upper crustal media in the northeastern Tibetan Plateau and adjacent areas.The principal compressive strain direction derived from GNSS is generally consistent with the polarization direction of fast S-waves,but there are also local tectonic regions with large differences between them,which reflect the different deformation mechanisms of regional upper crustal media.The combination of GNSS and seismic anisotropy data can reveal the depth variation characteristics of crustal deformation and deepen understanding of three-dimensional crustal deformation and the deep dynamical mechanisms underlying it.it.
基金The National Basic Research Program of China under contract Nos 2015CB453200,2013CB956200,2012CB957803 and2010CB950400the National Natural Science Foundation of China under contract Nos 41275086 and 41475070
文摘Long-term variations in a sea surface wind speed (WS) and a significant wave height (SWH) are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource exploitation, and other activities. The seasonal characteristics of the long-term trends in China's seas WS and SWH are determined based on 24 a (1988-2011) cross-calibrated, multi-platform (CCMP) wind data and 24 a hindcast wave data obtained with the WAVEWATCH-III (WW3) wave model forced by CCMP wind data. The results show the following. (1) For the past 24 a, the China's WS and SWH exhibit a significant increasing trend as a whole, of 3.38 cm/(s.a) in the WS, 1.3 cm/a in the SWH. (2) As a whole, the increasing trend of the China's seas WS and SWH is strongest in March-April-May (MAM) and December-January-February (DJF), followed by June-July-August (JJA), and smallest in September-October-November (SON). (3) The areal extent of significant increases in the WS was largest in MAM, while the area decreased in JJA and DJF; the smallest area was apparent in SON. In contrast to the WS, almost all of China's seas exhibited a significant increase in SWH in MAM and DJF; the range was slightly smaller in JJA and SON. The WS and SWH in the Bohai Sea, the Yellow Sea, East China Sea, the Tsushima Strait, the Taiwan Strait, the northern South China Sea, the Beibu Gull and the Gulf of Thailand exhibited a significant increase in all seasons. (4) The variations in China's seas SWH and WS depended on the season. The areas with a strong increase usually appeared in DJF.
基金funded by the National Science Centre,Poland(NCN)(Grant No.2020/37/N/ST10/01486).
文摘This paper presents the integration of seismic refraction and multichannel analysis of surface wave(MASW)measurements to investigate the anisotropy of P-and S-wave velocities.Additionally,synthetic forward modelling is presented as a tool for supporting seismic anisotropy studies.The geophysical measurements of cracks allowed to recognise the fracturing of a granite rock mass in a Paleozoic granite quarry(Strzegom,Poland)and a dolomite rock mass in a Triassic dolomite quarry(Podlesna,Poland).Application of the forward modelling supports the interpretation of seismic methods,simplifying data processing and verifying the final results based on data from difficult seismic conditions.As a result of direct measurements,two crack systems were determined in granite rock mass:NNE-SSW and NNW-SSE,and two in dolomite rock mass:NNE-SSW and NW-SE.Furthermore,the numerical results show the relationship between the highest values of P-and S-wave velocities and separated crack systems which allowed an unequivocal interpretation of the direction of stress,resulting in the deformations.The obtained information is promising to be helpful in mining exploration for optimising excavation works.
基金National Key Research and Development Program(2018YFC1505401,2018YFC1505404)the National Natural Science Foundation of China(41672283,41731285,41502299)+1 种基金Youth Fund Project of NSFC(Grants No.41907225)Open fund of State Key Laboratory of geological disaster prevention and geological environment protection(Grants No.SKLGP2018K011)for their strong support for this topic
文摘The"5.12"Wenchuan earthquake in 2008 triggered a large number of co-seismic landslides.The rear boundary or cracks of co-seismic landslide are generally located at the steep free surface of thin or thick mountains.Dynamic process of this kind of landslides could be divided into two parts:the seismic dynamic response of the slope and the movement process of rock mass.Taking the Laoyingyan rockslide as an example,the amplification effect was studied by single-degree-of-freedom system analysis method.Besides,the dynamic process of landslide under seismic loading was simulated by the finite difference method(FDM)and discrete element method(DEM).The amplification coefficient of the rockslide to seismic wave is 1.25.The results show that the critical sliding surface of the Laoyingyan rockslide was formed at the 23 th seconds under the action of seismic wave.At the same time,tension failure occurred at the rear edge of the sliding mass and shear failure occurred at the front edge.The maximum displacement was 0.81 m and the initial velocity was 2.78 m/s.During the initiation process of the rockslide,the rock mass firstly broke down along the joints which are along the dip of the rock stratum,and then collapsed bodily along the secondary structural planes.In the process of movement,the maximum velocity of rock mass was 38.24 m/s.After that,the rock mass underwent multiple collisions,including contact,deceleration to 0 and speed recovery after rebound.Finally,due to the constant loss of energy,the rocks stopped and accumulated loosely at the foot of the slope.The longest distance of movement was about 494 m.Besides,the smaller the damping ratio,the farther the rock mass moved.Compared with the results without considering the amplification factor,the movement distance of landslide by considering the amplification factor was more accurate.The study of the Laoyingyan rockslide is helpful to strengthen our field identification of potential co-seismic rockslides.At the same time,understanding its movement and accumulation process can help us better predict the hazard scope of the co-seismic rockslides,and provide a reference for the design of treatment projects.
文摘This study employs Landsat-8 Operational Land Imager (OLI) thermal infrared satellite data to compare land surface temperature of two cities in Ghana: Accra and Kumasi. These cities have human populations above 2 million and the corresponding anthropogenic impact on their environments significantly. Images were acquired with minimum cloud cover (<10%) from both dry and rainy seasons between December to August. Image preprocessing and rectification using ArcGIS 10.8 software w<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ere</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> used. The shapefiles of Accra and Kumasi were used to extract from the full scenes to subset the study area. Thermal band data numbers were converted to Top of Atmospheric Spectral Radiance using radiance rescaling factors. To determine the density of green on a patch of land, normalized difference vegetation index (NDVI) was calculated by using red and near-infrared bands </span><i><span style="font-family:Verdana;">i.e</span></i></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> Band 4 and Band 5. Land surface emissivity (LSE) was also calculated to determine the efficiency of transmitting thermal energy across the surface into the atmosphere. Results of the study show variation of temperatures between different locations in two urban areas. The study found Accra to have experienced higher and lower dry season and wet season temperatures, respectively. The temperature ranges corresponding to the dry and wet seasons were found to be 21.0985</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 46.1314</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;">, and, 18.3437</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 30.9693</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> respectively. Results of Kumasi also show a higher range of temperatures from 32.6986</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to 19.1077<span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> during the dry season. In the wet season, temperatures ranged from 26.4142</span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">-</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">0</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.898728</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;"><span style="color:#4F4F4F;font-family:Simsun;font-size:14px;white-space:normal;background-color:#FFFFFF;">o</span></span></span>C</span><span style="font-family:Verdana;">. Among the reasons for the cities of Accra and Kumasi recorded higher than corresponding rural areas’ values can be attributed to the urban heat islands’ phenomenon.</span></span></span></span>
基金supported by the National Natural Science Foundation of China (Grant No. 40730952)the National Basic Research Program of China (Grant No. 2009CB421405)the Program of Knowledge Innovation for the third period, the Chinese Academy of Sciences (Grant No. KZCX2-YW-220), and IAP07414
文摘The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant Nos.2021EEEVL0204 and 2018A02。
文摘As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete(RC)frame structure.Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance.Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions.A seismic fragility study of displacement demand is conducted based on numerical simulation.The acceleration response and displacement response of different combinations are compared.The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.
基金Project supported by the National Natural Science Foundation of China (Grant No 60571058)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No 20070701010)
文摘Composite electromagnetic scattering from a two-dimensional (2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain (FDTD) method. A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices.The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly. To validate the proposed numerical technique,a 2D infinitely long cylinder over the sea surface is taken into account first.The variation of angular distribution of the scattering changing with incident angle is calculated. The results show good agreement with the conventional moment method. Finally,the influence of the incident angle,the polarization,and the size of the ship-like target on the composite scattering coefficient is discussed in detail.