Grouting defects are an inherent challenge in construction practices,exerting a considerable impact on the operational structural integrity of connections.This investigation employed the impact-echo technique for the ...Grouting defects are an inherent challenge in construction practices,exerting a considerable impact on the operational structural integrity of connections.This investigation employed the impact-echo technique for the detection of grouting anomalies within connections,enhancing its precision through the integration of wavelet packet energy principles for damage identification purposes.A series of grouting completeness assessments were meticulously conducted,taking into account variables such as the divergent material properties of the sleeves and the configuration of adjacent reinforcement.The findings revealed that:(i)the energy distribution for the highstrength concrete cohort predominantly occupied the frequency bands 42,44,45,and 47,whereas for other groups,it was concentrated within the 37 to 40 frequency band;(ii)the delineation of empty sleeves was effectively discernible by examining the wavelet packet energy ratios across the spectrum of frequencies,albeit distinguishing between sleeves with 50%and full grouting density proved challenging;and(iii)the wavelet packet energy analysis yielded variable detection outcomes contingent on the material attributes of the sleeves,demonstrating heightened sensitivity when applied to ultrahigh-performance concrete matrices and GFRP-reinforced steel bars.展开更多
Grapevine is one of the most economically important crops worldwide.However,the previous versions of the grapevine reference genome tipically consist of thousands of fragments with missing centromeres and telomeres,li...Grapevine is one of the most economically important crops worldwide.However,the previous versions of the grapevine reference genome tipically consist of thousands of fragments with missing centromeres and telomeres,limiting the accessibility of the repetitive sequences,the centromeric and telomeric regions,and the study of inheritance of important agronomic traits in these regions.Here,we assembled a telomere-to-telomere(T2T)gap-free reference genome for the cultivar PN40024 using PacBio HiFi long reads.The T2T reference genome(PN_T2T)is 69 Mb longer with 9018 more genes identified than the 12X.v0 version.We annotated 67%repetitive sequences,19 centromeres and 36 telomeres,and incorporated gene annotations of previous versions into the PN_T2T assembly.We detected a total of 377 gene clusters,which showed associations with complex traits,such as aroma and disease resistance.Even though PN40024 derives from nine generations of selfing,we still found nine genomic hotspots of heterozygous sites associated with biological processes,such as the oxidation–reduction process and protein phosphorylation.The fully annotated complete reference genome therefore constitutes an important resource for grapevine genetic studies and breeding programs.展开更多
WiFi has become one of the most popular ways to access the Internet.However,in large-scale campus wireless networks,it is challenging for network administrators to provide optimized access quality without knowledge on...WiFi has become one of the most popular ways to access the Internet.However,in large-scale campus wireless networks,it is challenging for network administrators to provide optimized access quality without knowledge on fine-grained traffic characteristics and real network performance.In this paper,we implement PerfMon,a network performance measurement and diagnosis system,which integrates collected multi-source datasets and analysis methods.Based on PerfMon,we first conduct a comprehensive measurement on application-level traffic patterns and behaviors from multiple dimensions in the wireless network of T university(TWLAN),which is one of the largest campus wireless networks.Then we systematically study the application-level network performance.We observe that the application-level traffic behaviors and performance vary greatly across different locations and device types.The performance is far from satisfactory in some cases.To diagnose these problems,we distinguish locations and device types,and further locate the most crucial factors that affect the performance.The results of case studies show that the influential factors can effectively characterize performance changes and explain for performance degradation.展开更多
The forming limit diagram plays an important role in predicting the forming limit of sheet metals.Previous studies have shown that,the method to construct the forming limit diagram based on instability theory of the o...The forming limit diagram plays an important role in predicting the forming limit of sheet metals.Previous studies have shown that,the method to construct the forming limit diagram based on instability theory of the original shear failure criterion is efective and simple.The original shear instability criterion can accurately predict the left area of the forming limit diagram but not the right area.In this study,in order to improve the accuracy of the original shear failure criterion,a modifed shear failure criterion was proposed based on in-depth analysis of the original shear failure criterion.The detailed improvement strategies of the shear failure criterion and the complete calculation process are given.Based on the modifed shear failure criterion and diferent constitutive equations,the theoretical forming limit of TRIP780 steel and 5754O aluminum alloy sheet metals are calculated.By comparing the theoretical and experimental results,it is shown that proposed modifed shear failure criterion can predict the right area of forming limit more reasonably than the original shear failure criterion.The efect of the pre-strain and constitutive equation on the forming limits are also analyzed in depth.The modifed shear failure criterion proposed in this study provides an alternative and reliable method to predict forming limit of sheet metals.展开更多
An isolation trench is a simple and effective method to isolate structural vibrations originating from sources of vibration other than earthquakes(machines,traffic,explosions,etc.);however,there is still not a conclus...An isolation trench is a simple and effective method to isolate structural vibrations originating from sources of vibration other than earthquakes(machines,traffic,explosions,etc.);however,there is still not a conclusive depth of the isolation trench for frame structures.To investigate the isolation effect of a trench in the frame structure designed for ground vibration,both a field test and finite element analysis were conducted to analyze the reduced effect of the vibration.The vibration reduction analysis was based on the dynamic equation and wave theory.Considering the vibration control of an industrial plant frame,a soil-trench-building finite element model was built to analyze the vibration characteristics of the floor before and after the open isolation trench structure was used.According to the model,a dynamic test was carried out on the frame structure to assess the effect of the vibration reduction by introducing the trench.The results showed that the depth of the trench was the dominating factor in vibration isolation.When the depth of the trench reached 1~1.3 times the wavelength of the Rayleigh wave,the damping effect was the strongest.the width of the trench has little effect on the vibration isolation efficiency,and the trench must be maintained at a certain distance from the building to ensure the vibration damping efficiency.The vibration of each floor was obviously reduced after the trench was built.The vibration damping effect of the trench was significant.展开更多
Multi-stages volcanic are available in HX area, shielding the seismic waves. Previous seismic acquisitions of large size bin, less fold coverage and narrow azimuth result in indistinct fault images, low S/N ratio and ...Multi-stages volcanic are available in HX area, shielding the seismic waves. Previous seismic acquisitions of large size bin, less fold coverage and narrow azimuth result in indistinct fault images, low S/N ratio and the difficulty of multi-stages volcanic characterization. In reference to the successful experience of domestic and overseas volcanic exploration, the low frequency excitation and receiving, and survey with wide range, high coverage, wide azimuth should be paid more attention, associated with two-dimensional and three-dimensional wave equation forward modeling and real data processing contrast analysis method. The image of underlying strata and fault are remarkably improved in the new method, according to the processing results of new seismic data. The new method will provide technical reference for the similar volcanic development area in the future seismic acquisition design.展开更多
Terrain is an important environment factor that plays a vital role in human development by influencing the spatial layout of land use patterns.The terrain niche index,combined with slope and elevation,can comprehensiv...Terrain is an important environment factor that plays a vital role in human development by influencing the spatial layout of land use patterns.The terrain niche index,combined with slope and elevation,can comprehensively present detailed information about spatial differences in terrain and is superior to single terrain factors.We applied remote sensing and geographical information system to terrain gradient,used the non-dimensional distribution index to examine spatial distribution characteristics of various landscape types,and analyzed the ecological effects of landscape were quantitatively on terrain gradients.Eco-environment quality(EEQ) was evaluated using the forestry operation area as the evaluation unit.The spatial distributions in various landscapes were significantly influenced by terrain factors,especially by bodies of water,cropland and residential land.The spatial distribution varied greatly in different terrain gradients for similar landscape types.The areas associated with good,intermediate and poor EEQ were occupied primarily by natural landscape,semi-natural and largely artificial landscapes,respectively.展开更多
In order to provide reference for the selection of appropriate pollination varieties facilitating the improvement of the flavor quality of bagged Fuji apple,the metaxenia effects of 5 pollination varieties on sugars,o...In order to provide reference for the selection of appropriate pollination varieties facilitating the improvement of the flavor quality of bagged Fuji apple,the metaxenia effects of 5 pollination varieties on sugars,organic acids and flavor quality of bagged Fuji fruit were studied.The results showed that the 5 pollination varieties had significant metaxenia effects on sugars,organic acids and flavor quality of bagged Fuji fruit.For the sugar components,the fruits pollinated with Golden Delicious and Jinxiuhaitang showed higher glucose contents,and the fruit pollinated with Gala had the highest sucrose content;the fruits pollinated by Gala,Golden Delicious and Ruby exhibited higher malic acids,and the oxalic acid content and the succinic acid content were higher in the fruits pollinated with Jinxiuhaitang and Ruby;and the fruit pollinated with Gala had the highest total sugar content,and the total acid content was higher in the fruits pollinated by Jinxiuhaitang and Ruby.The sugar-acid ratio was higher in the fruits pollinated with Gala and Golden Delicious,and the lowest in the fruit pollinated with Ruby.The sensory evaluation of fruits showed that the fruit pollinated with Ruby tasted sour-sweet,while the fruits pollinated with other 4 pollination varieties were sour and sweet moderately.展开更多
Earings appear easily during deep drawing of cylindrical parts owing to the anisotropic properties of materials.However,current methods cannot fully utilize the mechanical properties of material,and the number of eari...Earings appear easily during deep drawing of cylindrical parts owing to the anisotropic properties of materials.However,current methods cannot fully utilize the mechanical properties of material,and the number of earings obtained differ with the simulation methods.In order to predict the eight-earing problem in the cylindrical deep drawing of 5754O aluminum alloy sheet,a new method of combining the yield stress and anisotropy index(r-value)to solve the parameters of the Hil 148 yield function is proposed.The general formula for the yield stress and r-value in any direction is presented.Taking a 5754O aluminum alloy sheet as an example in this study,the deformation area in deep drawing is divided into several equal sectorial regions based on the anisotropy.The parameters of the Hill48 yield function are solved based on the yield stress and r-value simultaneously for the corresponding deformation area.Finite element simulations of deep drawing based on new and existing methods are carried out for comparison with experimental results.This study provides a convenient and reliable way to predict the formation of eight earings in the deep drawing process,which is expected to be useful in industrial applications.The results of this study lay the foundation for the optimization of the cylindrical deep drawing process,including the optimization of the blank shape to eliminate earing defects on the final product,which is of great importance in the actual production process.展开更多
Based on the rigid plastic theory, the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parall...Based on the rigid plastic theory, the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parallel rigid plates. The non-dimensional load-deflection responses predicted by the present theory and the finite element simulations are compared, and the favorable agreement is found. The results show that strain hardening may have a noticeable influence on the load-deflection curves of an elliptical tube under quasi-static compression. Compared with the circular counterpart, the elliptical tube exhibits different energy absorption behavior due to the difference between the major axis and the minor axis. When loaded along the major axis of a slightly oval tube,a relative even and long plateau region of the load-deflection curve is achieved, which is especially desirable for the design of energy absorbers.展开更多
An analytical model is developed to study the crushing behavior and energy absorption capability of a single elliptical tube impacted by two parallel rigid plates,with and without consideration of the strain hardening...An analytical model is developed to study the crushing behavior and energy absorption capability of a single elliptical tube impacted by two parallel rigid plates,with and without consideration of the strain hardening effect. The four-hinge collapse mechanism is used, and the governing equation is derived from Lagrange equations of the second kind. The numerical simulation of the dynamic response of the elliptical tube under impact using the finite element explicit code LS-DYNA is performed. The reaction force-displacement curve and displacement-time curve of the plate obtained from the two methods are in good agreement.展开更多
[Objectives]This study was conducted to improve the genetic transformation rate of maize. [Methods]The seeds of maize " Zheng 58" as the experimental material were germinated and treated under freezing tempe...[Objectives]This study was conducted to improve the genetic transformation rate of maize. [Methods]The seeds of maize " Zheng 58" as the experimental material were germinated and treated under freezing temperature of-18 ℃ for 30 and 35 min. The EGFP gene was transformed into the growth points of these seed buds by Agrobacterium tumefaciens EHA105. The transformation effect was determined by fluorescence protein detection on transformed buds. [Results]After a certain period of treatment at-18 ℃ following germination and transformation of maize bud growth points with A. tumefaciens,although the survival rate of maize buds was reduced,the percentage of transformed cells significantly increased. [Conclusions]Low temperature treatment can improve the transformation efficiency of A. tumefaciens to the growth point of maize bud.展开更多
Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spec...Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer(FTS)EM27/SUN.This data set is used to assess the characteristics of combustion-related CO_(2)emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO_(2)(e.g.,ΔXCO andΔXCO_(2)).The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites.The ratio ofΔXCO overΔXCO_(2)(ΔXCO:ΔXCO_(2))is used to estimate the combustion efficiency in the Beijing region.A high correlation coefficient(0.86)betweenΔXCO andΔXCO_(2)is observed.The CO:CO_(2)emission ratio estimated from inventories is higher than the observedΔXCO:ΔXCO_(2)(10.46±0.11 ppb ppm^(−1))by 42.54%-101.15%,indicating an underestimation in combustion efficiency in the inventories.DailyΔXCO:ΔXCO_(2)are influenced by transportation governed by weather conditions,except for days in summer when the correlation is low due to the terrestrial biotic activity.By convolving the column footprint[ppm(μmol m-2 s-1)-1]generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models(WRF-X-STILT)with two fossil-fuel emission inventories(the Multi-resolution Emission Inventory for China(MEIC)and the Peking University(PKU)inventory),the observed enhancements of CO_(2)and CO were used to evaluate the regional emissions.The CO_(2)emissions appear to be underestimated by 11%and 49%for the MEIC and PKU inventories,respectively,while CO emissions were overestimated by MEIC(30%)and PKU(35%)in the Beijing area.展开更多
Objective:Limited evidence is available regarding the associations of centralization with gastric cancer patients’quality of care in high surgical volume settings.The current study aimed to explore the effects of hos...Objective:Limited evidence is available regarding the associations of centralization with gastric cancer patients’quality of care in high surgical volume settings.The current study aimed to explore the effects of hospital volume and the Herfindahl-Hirschman index(HHI)on in-hospital mortality,total cost,and length of stay for Chinese gastrectomy patients in a nationwide database.Methods:We extracted data on gastrectomy for gastric cancer from the Hospital Quality Monitoring System Database between 2013 and 2018.Hospital volume was divided into 4 quartiles:low(1-83 cases per year),medium(84-238 cases),high(239-579 cases),and very high(580-1,193 cases).The HHI was divided into 3 categories:highly concentrated(>2,500),moderately concentrated(1,500-2,500),and unconcentrated(<1,500).We used mixed-effects models to analyze the data while accounting for data clustering.Results:We analyzed 125,683 patients in 515 institutions.In the multivariable analyses,hospital volume was significantly associated with in-hospital mortality[medium vs.low:odds ratio(OR)=0.61,95%confidence interval(95%CI)=0.43-0.84,P=0.003;high:OR=0.57,95%CI=0.38-0.87,P=0.009;and very high:OR=0.33,95%CI=0.18-0.61,P<0.001)and length of stay(high vs.low:β=-0.036,95%CI=-0.071--0.002,P=0.039)but not with total cost.Hospitals located in unconcentrated provinces had higher in-hospital mortality(OR=1.52,95%CI=1.03-2.26,P=0.036)and longer lengths of stay(β=0.024,95%CI=0.001-0.047,P=0.041)than hospitals located in highly concentrated provinces.Conclusions:Centralization of gastrectomy,measured by hospital volume and the HHI,was associated with decreased in-hospital mortality and shortened length of stay without increasing total cost.These results support the strategy of centralizing gastrectomy in high-volume settings.展开更多
Wheat-rye T1BL·1RS translocation lines are widely used,especially in China,but their processing quality is generally poor.An interfering expression vector targeting theω-secalin genes was constructed with the 1B...Wheat-rye T1BL·1RS translocation lines are widely used,especially in China,but their processing quality is generally poor.An interfering expression vector targeting theω-secalin genes was constructed with the 1Bx7 seed-specific promoter.Biolistic-mediated genetic transformation of the wheat cultivar KN199 carrying the T1BL·1RS translocation generated 10 transgenic lines.Two representative transgenic lines,8-2 and 13-7,were selected for analysis.Compared with the control,the two transformants showed an up to 4.5-fold decrease in totalω-secalins and various levels of decrease inω-gliadins,γ-gliadins,and low-molecular-weight glutenins.A decrease in high molecular weight(HMW)glutenin 1Bx7 was detected only in 8-2,owing possibly to promoter methylation.Increased levels ofα-gliadins were observed in both transformants,but increased levels of HMW glutenins were observed only in 13-7.Line 13-7 showed increases in gluten index,Zeleny sedimentation value,stabilization time,and maximum resistance.Its bread volume was 849.6 mL,an 11.9%increase over that of the control.Line 8-2 showed decreases in these parameters,but its total cake-making quality score was 88,an 17.3%increase over that of the control.The study demonstrates that the same RNAi construct may produce different effects on wheat processing quality and highlights the influence of the vector promoter in RNA interference.展开更多
Grasslands and agro-ecosystems occupy one-third of the global terrestrial area.However,great uncertainty still exists about their contributions to the global carbon cycle.This study used various combinations of a simp...Grasslands and agro-ecosystems occupy one-third of the global terrestrial area.However,great uncertainty still exists about their contributions to the global carbon cycle.This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors,specifically radiation,temperature,and moisture,on the ecosystem carbon exchange at two dissimilar study sites.Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases,we investigated the response characteristics of productivity of grasslands and croplands to different environmental factors,and analyzed the seasonal change patterns of different model parameters.Parameter estimations and uncertainty analyses were performed based on a Bayesian approach.Our results indicated that:(1) the net ecosystem exchange(NEE) of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns.On the whole,the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO2;(2) in the daytime,the mean NEE of the two ecosystems had the largest values in July and the lowest values in October.However,overall carbon uptake in the cropland was greater than in the alpine meadow from June to September;(3) at the alpine meadow site,temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season,while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region;(4) at the cropland site,both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and(5) some parameters had an obvious characteristic of seasonal patterns,while others had only small seasonal variations.展开更多
基金supported by financial support from the National Natural Science Foundation of China(U1904177)the Excellent Youth Natural Science Foundation of Henan Province of China(212300410079)+2 种基金the Subproject of the Key Project of the National Development and Reform Commission of China(202203001)the Project of Young Key Teachers in Henan Province of China(2019GGJS01)Horizontal Research Projects(20230352A).
文摘Grouting defects are an inherent challenge in construction practices,exerting a considerable impact on the operational structural integrity of connections.This investigation employed the impact-echo technique for the detection of grouting anomalies within connections,enhancing its precision through the integration of wavelet packet energy principles for damage identification purposes.A series of grouting completeness assessments were meticulously conducted,taking into account variables such as the divergent material properties of the sleeves and the configuration of adjacent reinforcement.The findings revealed that:(i)the energy distribution for the highstrength concrete cohort predominantly occupied the frequency bands 42,44,45,and 47,whereas for other groups,it was concentrated within the 37 to 40 frequency band;(ii)the delineation of empty sleeves was effectively discernible by examining the wavelet packet energy ratios across the spectrum of frequencies,albeit distinguishing between sleeves with 50%and full grouting density proved challenging;and(iii)the wavelet packet energy analysis yielded variable detection outcomes contingent on the material attributes of the sleeves,demonstrating heightened sensitivity when applied to ultrahigh-performance concrete matrices and GFRP-reinforced steel bars.
基金This work was supported by the National Natural Science Fund for Excellent Young Scientists Fund Program(Overseas)to Y.Z.,the National Key Research and Development Program of China(grant 2019YFA0906200)the Agricultural Science and Technology Innovation Program(CAAS-ZDRW202101)+1 种基金the Shenzhen Science and Technology Program(grant KQTD2016113010482651)the BMBF-funded de.
文摘Grapevine is one of the most economically important crops worldwide.However,the previous versions of the grapevine reference genome tipically consist of thousands of fragments with missing centromeres and telomeres,limiting the accessibility of the repetitive sequences,the centromeric and telomeric regions,and the study of inheritance of important agronomic traits in these regions.Here,we assembled a telomere-to-telomere(T2T)gap-free reference genome for the cultivar PN40024 using PacBio HiFi long reads.The T2T reference genome(PN_T2T)is 69 Mb longer with 9018 more genes identified than the 12X.v0 version.We annotated 67%repetitive sequences,19 centromeres and 36 telomeres,and incorporated gene annotations of previous versions into the PN_T2T assembly.We detected a total of 377 gene clusters,which showed associations with complex traits,such as aroma and disease resistance.Even though PN40024 derives from nine generations of selfing,we still found nine genomic hotspots of heterozygous sites associated with biological processes,such as the oxidation–reduction process and protein phosphorylation.The fully annotated complete reference genome therefore constitutes an important resource for grapevine genetic studies and breeding programs.
基金supported by the National Key Research and Development Program of China(No.2020YFE0200500)。
文摘WiFi has become one of the most popular ways to access the Internet.However,in large-scale campus wireless networks,it is challenging for network administrators to provide optimized access quality without knowledge on fine-grained traffic characteristics and real network performance.In this paper,we implement PerfMon,a network performance measurement and diagnosis system,which integrates collected multi-source datasets and analysis methods.Based on PerfMon,we first conduct a comprehensive measurement on application-level traffic patterns and behaviors from multiple dimensions in the wireless network of T university(TWLAN),which is one of the largest campus wireless networks.Then we systematically study the application-level network performance.We observe that the application-level traffic behaviors and performance vary greatly across different locations and device types.The performance is far from satisfactory in some cases.To diagnose these problems,we distinguish locations and device types,and further locate the most crucial factors that affect the performance.The results of case studies show that the influential factors can effectively characterize performance changes and explain for performance degradation.
基金Supported by R&D Program of Beijing Municipal Education Commission of China(Grant No.KZ200010009041)Beijing Municipal University Youth Top Talents Training Program of China(Grant No.CIT&TCD201704014)Natural Science Foundation of China(Grant No.51475003).
文摘The forming limit diagram plays an important role in predicting the forming limit of sheet metals.Previous studies have shown that,the method to construct the forming limit diagram based on instability theory of the original shear failure criterion is efective and simple.The original shear instability criterion can accurately predict the left area of the forming limit diagram but not the right area.In this study,in order to improve the accuracy of the original shear failure criterion,a modifed shear failure criterion was proposed based on in-depth analysis of the original shear failure criterion.The detailed improvement strategies of the shear failure criterion and the complete calculation process are given.Based on the modifed shear failure criterion and diferent constitutive equations,the theoretical forming limit of TRIP780 steel and 5754O aluminum alloy sheet metals are calculated.By comparing the theoretical and experimental results,it is shown that proposed modifed shear failure criterion can predict the right area of forming limit more reasonably than the original shear failure criterion.The efect of the pre-strain and constitutive equation on the forming limits are also analyzed in depth.The modifed shear failure criterion proposed in this study provides an alternative and reliable method to predict forming limit of sheet metals.
基金National Natural Science Foundation of China(U1904177)Key R&D Projects of the Ministry of Transport(2018-MS5-136)Henan Province Transportation Science and Technology Plan Project(2018J2,2019J-2-10).
文摘An isolation trench is a simple and effective method to isolate structural vibrations originating from sources of vibration other than earthquakes(machines,traffic,explosions,etc.);however,there is still not a conclusive depth of the isolation trench for frame structures.To investigate the isolation effect of a trench in the frame structure designed for ground vibration,both a field test and finite element analysis were conducted to analyze the reduced effect of the vibration.The vibration reduction analysis was based on the dynamic equation and wave theory.Considering the vibration control of an industrial plant frame,a soil-trench-building finite element model was built to analyze the vibration characteristics of the floor before and after the open isolation trench structure was used.According to the model,a dynamic test was carried out on the frame structure to assess the effect of the vibration reduction by introducing the trench.The results showed that the depth of the trench was the dominating factor in vibration isolation.When the depth of the trench reached 1~1.3 times the wavelength of the Rayleigh wave,the damping effect was the strongest.the width of the trench has little effect on the vibration isolation efficiency,and the trench must be maintained at a certain distance from the building to ensure the vibration damping efficiency.The vibration of each floor was obviously reduced after the trench was built.The vibration damping effect of the trench was significant.
文摘Multi-stages volcanic are available in HX area, shielding the seismic waves. Previous seismic acquisitions of large size bin, less fold coverage and narrow azimuth result in indistinct fault images, low S/N ratio and the difficulty of multi-stages volcanic characterization. In reference to the successful experience of domestic and overseas volcanic exploration, the low frequency excitation and receiving, and survey with wide range, high coverage, wide azimuth should be paid more attention, associated with two-dimensional and three-dimensional wave equation forward modeling and real data processing contrast analysis method. The image of underlying strata and fault are remarkably improved in the new method, according to the processing results of new seismic data. The new method will provide technical reference for the similar volcanic development area in the future seismic acquisition design.
基金supported by National High Technology Research and Development Program 863(Grant No.2012AA102001)Natural Scientific Foundation of Heilongjiang Province(Grant No.D201410)Natural Science Foundation of Heilongjiang Province Department Education Commission(Grant No.12531513)
文摘Terrain is an important environment factor that plays a vital role in human development by influencing the spatial layout of land use patterns.The terrain niche index,combined with slope and elevation,can comprehensively present detailed information about spatial differences in terrain and is superior to single terrain factors.We applied remote sensing and geographical information system to terrain gradient,used the non-dimensional distribution index to examine spatial distribution characteristics of various landscape types,and analyzed the ecological effects of landscape were quantitatively on terrain gradients.Eco-environment quality(EEQ) was evaluated using the forestry operation area as the evaluation unit.The spatial distributions in various landscapes were significantly influenced by terrain factors,especially by bodies of water,cropland and residential land.The spatial distribution varied greatly in different terrain gradients for similar landscape types.The areas associated with good,intermediate and poor EEQ were occupied primarily by natural landscape,semi-natural and largely artificial landscapes,respectively.
基金Supported by Major Agricultural Applied Technology Innovation Project of Shandong Province(2014)Agricultural Science and Technology Innovation Project of Shandong Academy of Agricultural Sciences(CXGC2016B07)Earmarked Fund for China Agriculture Research System(CARS-28)
文摘In order to provide reference for the selection of appropriate pollination varieties facilitating the improvement of the flavor quality of bagged Fuji apple,the metaxenia effects of 5 pollination varieties on sugars,organic acids and flavor quality of bagged Fuji fruit were studied.The results showed that the 5 pollination varieties had significant metaxenia effects on sugars,organic acids and flavor quality of bagged Fuji fruit.For the sugar components,the fruits pollinated with Golden Delicious and Jinxiuhaitang showed higher glucose contents,and the fruit pollinated with Gala had the highest sucrose content;the fruits pollinated by Gala,Golden Delicious and Ruby exhibited higher malic acids,and the oxalic acid content and the succinic acid content were higher in the fruits pollinated with Jinxiuhaitang and Ruby;and the fruit pollinated with Gala had the highest total sugar content,and the total acid content was higher in the fruits pollinated by Jinxiuhaitang and Ruby.The sugar-acid ratio was higher in the fruits pollinated with Gala and Golden Delicious,and the lowest in the fruit pollinated with Ruby.The sensory evaluation of fruits showed that the fruit pollinated with Ruby tasted sour-sweet,while the fruits pollinated with other 4 pollination varieties were sour and sweet moderately.
基金Supported by National Natural Science Foundation of China(Grant No.51475003)Beijing Youth Top Talents Training Program
文摘Earings appear easily during deep drawing of cylindrical parts owing to the anisotropic properties of materials.However,current methods cannot fully utilize the mechanical properties of material,and the number of earings obtained differ with the simulation methods.In order to predict the eight-earing problem in the cylindrical deep drawing of 5754O aluminum alloy sheet,a new method of combining the yield stress and anisotropy index(r-value)to solve the parameters of the Hil 148 yield function is proposed.The general formula for the yield stress and r-value in any direction is presented.Taking a 5754O aluminum alloy sheet as an example in this study,the deformation area in deep drawing is divided into several equal sectorial regions based on the anisotropy.The parameters of the Hill48 yield function are solved based on the yield stress and r-value simultaneously for the corresponding deformation area.Finite element simulations of deep drawing based on new and existing methods are carried out for comparison with experimental results.This study provides a convenient and reliable way to predict the formation of eight earings in the deep drawing process,which is expected to be useful in industrial applications.The results of this study lay the foundation for the optimization of the cylindrical deep drawing process,including the optimization of the blank shape to eliminate earing defects on the final product,which is of great importance in the actual production process.
基金Project supported by the National Natural Science Foundation of China(No.11472035)
文摘Based on the rigid plastic theory, the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parallel rigid plates. The non-dimensional load-deflection responses predicted by the present theory and the finite element simulations are compared, and the favorable agreement is found. The results show that strain hardening may have a noticeable influence on the load-deflection curves of an elliptical tube under quasi-static compression. Compared with the circular counterpart, the elliptical tube exhibits different energy absorption behavior due to the difference between the major axis and the minor axis. When loaded along the major axis of a slightly oval tube,a relative even and long plateau region of the load-deflection curve is achieved, which is especially desirable for the design of energy absorbers.
基金Project supported by the National Natural Science Foundation of China(No.11032001)
文摘An analytical model is developed to study the crushing behavior and energy absorption capability of a single elliptical tube impacted by two parallel rigid plates,with and without consideration of the strain hardening effect. The four-hinge collapse mechanism is used, and the governing equation is derived from Lagrange equations of the second kind. The numerical simulation of the dynamic response of the elliptical tube under impact using the finite element explicit code LS-DYNA is performed. The reaction force-displacement curve and displacement-time curve of the plate obtained from the two methods are in good agreement.
基金Supported by Natural Science Foundation of Hebei Province(C2017301071)Financial Project of Hebei Province(2017039339)
文摘[Objectives]This study was conducted to improve the genetic transformation rate of maize. [Methods]The seeds of maize " Zheng 58" as the experimental material were germinated and treated under freezing temperature of-18 ℃ for 30 and 35 min. The EGFP gene was transformed into the growth points of these seed buds by Agrobacterium tumefaciens EHA105. The transformation effect was determined by fluorescence protein detection on transformed buds. [Results]After a certain period of treatment at-18 ℃ following germination and transformation of maize bud growth points with A. tumefaciens,although the survival rate of maize buds was reduced,the percentage of transformed cells significantly increased. [Conclusions]Low temperature treatment can improve the transformation efficiency of A. tumefaciens to the growth point of maize bud.
基金supported by grants from the National Key Research and Development Program of China(Grant No.2017YFB0504000)National Natural Science Foundation of China(Grant No.41875043)+2 种基金the Strategic Priority Research 275 Program of the Chinese Academy of Sciences(Grant No.XDA17010102)External Cooperation Program of the Chinese Academy of Science(Grant No.GJHZ1802)Youth Innovation Promotion Association,CAS.
文摘Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide,CO_(2)(XCO_(2))and CO(XCO),were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer(FTS)EM27/SUN.This data set is used to assess the characteristics of combustion-related CO_(2)emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO_(2)(e.g.,ΔXCO andΔXCO_(2)).The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites.The ratio ofΔXCO overΔXCO_(2)(ΔXCO:ΔXCO_(2))is used to estimate the combustion efficiency in the Beijing region.A high correlation coefficient(0.86)betweenΔXCO andΔXCO_(2)is observed.The CO:CO_(2)emission ratio estimated from inventories is higher than the observedΔXCO:ΔXCO_(2)(10.46±0.11 ppb ppm^(−1))by 42.54%-101.15%,indicating an underestimation in combustion efficiency in the inventories.DailyΔXCO:ΔXCO_(2)are influenced by transportation governed by weather conditions,except for days in summer when the correlation is low due to the terrestrial biotic activity.By convolving the column footprint[ppm(μmol m-2 s-1)-1]generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models(WRF-X-STILT)with two fossil-fuel emission inventories(the Multi-resolution Emission Inventory for China(MEIC)and the Peking University(PKU)inventory),the observed enhancements of CO_(2)and CO were used to evaluate the regional emissions.The CO_(2)emissions appear to be underestimated by 11%and 49%for the MEIC and PKU inventories,respectively,while CO emissions were overestimated by MEIC(30%)and PKU(35%)in the Beijing area.
基金supported by Beijing Scholar Project 20182024(No.B00033)。
文摘Objective:Limited evidence is available regarding the associations of centralization with gastric cancer patients’quality of care in high surgical volume settings.The current study aimed to explore the effects of hospital volume and the Herfindahl-Hirschman index(HHI)on in-hospital mortality,total cost,and length of stay for Chinese gastrectomy patients in a nationwide database.Methods:We extracted data on gastrectomy for gastric cancer from the Hospital Quality Monitoring System Database between 2013 and 2018.Hospital volume was divided into 4 quartiles:low(1-83 cases per year),medium(84-238 cases),high(239-579 cases),and very high(580-1,193 cases).The HHI was divided into 3 categories:highly concentrated(>2,500),moderately concentrated(1,500-2,500),and unconcentrated(<1,500).We used mixed-effects models to analyze the data while accounting for data clustering.Results:We analyzed 125,683 patients in 515 institutions.In the multivariable analyses,hospital volume was significantly associated with in-hospital mortality[medium vs.low:odds ratio(OR)=0.61,95%confidence interval(95%CI)=0.43-0.84,P=0.003;high:OR=0.57,95%CI=0.38-0.87,P=0.009;and very high:OR=0.33,95%CI=0.18-0.61,P<0.001)and length of stay(high vs.low:β=-0.036,95%CI=-0.071--0.002,P=0.039)but not with total cost.Hospitals located in unconcentrated provinces had higher in-hospital mortality(OR=1.52,95%CI=1.03-2.26,P=0.036)and longer lengths of stay(β=0.024,95%CI=0.001-0.047,P=0.041)than hospitals located in highly concentrated provinces.Conclusions:Centralization of gastrectomy,measured by hospital volume and the HHI,was associated with decreased in-hospital mortality and shortened length of stay without increasing total cost.These results support the strategy of centralizing gastrectomy in high-volume settings.
基金The financial support by Key Research and Development Plan of Hebei Province(20326348D)Hebei Modern Agricultural Science and Technology Innovation Project(2019-4-08-1)are gratefully acknowledged.
文摘Wheat-rye T1BL·1RS translocation lines are widely used,especially in China,but their processing quality is generally poor.An interfering expression vector targeting theω-secalin genes was constructed with the 1Bx7 seed-specific promoter.Biolistic-mediated genetic transformation of the wheat cultivar KN199 carrying the T1BL·1RS translocation generated 10 transgenic lines.Two representative transgenic lines,8-2 and 13-7,were selected for analysis.Compared with the control,the two transformants showed an up to 4.5-fold decrease in totalω-secalins and various levels of decrease inω-gliadins,γ-gliadins,and low-molecular-weight glutenins.A decrease in high molecular weight(HMW)glutenin 1Bx7 was detected only in 8-2,owing possibly to promoter methylation.Increased levels ofα-gliadins were observed in both transformants,but increased levels of HMW glutenins were observed only in 13-7.Line 13-7 showed increases in gluten index,Zeleny sedimentation value,stabilization time,and maximum resistance.Its bread volume was 849.6 mL,an 11.9%increase over that of the control.Line 8-2 showed decreases in these parameters,but its total cake-making quality score was 88,an 17.3%increase over that of the control.The study demonstrates that the same RNAi construct may produce different effects on wheat processing quality and highlights the influence of the vector promoter in RNA interference.
基金funded by the National Natural Science Foundation of China(Nos.41401412,91125004)the Foundation for Excellent Youth Scholars of CAREERI,CAS(No.51Y451271)the Open Fund of the Key Laboratory of Desert and Desertification,CAS(No.KLDD-2014-007)
文摘Grasslands and agro-ecosystems occupy one-third of the global terrestrial area.However,great uncertainty still exists about their contributions to the global carbon cycle.This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors,specifically radiation,temperature,and moisture,on the ecosystem carbon exchange at two dissimilar study sites.Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases,we investigated the response characteristics of productivity of grasslands and croplands to different environmental factors,and analyzed the seasonal change patterns of different model parameters.Parameter estimations and uncertainty analyses were performed based on a Bayesian approach.Our results indicated that:(1) the net ecosystem exchange(NEE) of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns.On the whole,the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO2;(2) in the daytime,the mean NEE of the two ecosystems had the largest values in July and the lowest values in October.However,overall carbon uptake in the cropland was greater than in the alpine meadow from June to September;(3) at the alpine meadow site,temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season,while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region;(4) at the cropland site,both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and(5) some parameters had an obvious characteristic of seasonal patterns,while others had only small seasonal variations.
