Atmospheric carbon dioxide is an important kind of greenhouse gas which influences global temperature. Its concentration variation could indicate the distribution of human and natural activities in various regions. Th...Atmospheric carbon dioxide is an important kind of greenhouse gas which influences global temperature. Its concentration variation could indicate the distribution of human and natural activities in various regions. Through the non-dispersive infrared method, flask sampling of atmospheric CO2 concen- tration was measured weekly at four national background stations including Waliguan, Shangdianzi, Lin’an, and Longfengshan. Based on the data collected from September 2006 to August 2007, along with the Waliguan station’s experience on in situ observational data processing, the selection methods for sampling data through the atmospheric background CO2 concentration analysis were preliminarily discussed. On the basis of this result, the variation features of the four typical regions’ atmospheric background CO2 concentration was analyzed for the first time. The results show that the atmospheric CO2 concentration at Waliguan, Shangdianzi, Lin’an, and Longfengshan is 383.5, 385.9, 387.8, and 384.3 ppm, respectively. During the research period, CO2 concentration at the Waliguan station changed slightly. However, the CO2 concentration changed sharply at the Shangdianzi and the Lin’an stations due to the great influence of human activities in the Jingjinji and the Changjiang Delta economic zones, and changed regularly with seasons at Longfengshan station under dual influences of human activities and plant photosynthesis. The results from this study can lay the foundation for more profound studies on atmospheric CO2 concentration level of different areas in China, and could be used to improve the understanding of carbon source and sink distribution.展开更多
Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sink...Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.展开更多
Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate...Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char （APTC） for Rhodamine B （RhB）. Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics.展开更多
Objective： Diagnostic laparoscopy is recommended for the pretherapeutic staging of gastric cancer to detect any unexpected or unconfirmed intra-abdominal metastasis. The aim of this study was to evaluate the role and...Objective： Diagnostic laparoscopy is recommended for the pretherapeutic staging of gastric cancer to detect any unexpected or unconfirmed intra-abdominal metastasis. The aim of this study was to evaluate the role and indications of diagnostic laparoscopy in the detection of intra-abdominal metastasis. Methods： Standard diagnostic laparoscopy with peritoneal cytology examination was performed prospectively on patients who were clinically diagnosed with primary local advanced gastric cancer （CT≥2M0）. We calculated the rate of intra-abdominal metastases identified by diagnostic laparoscopy, and examined the relationship between peritoneal dissemination （P） and cytology results （CY）. Split-sample method was applied to find clinical risk factors for intra-abdominal metastasis. Multivariate logistic regression analysis and receiver-operator characteristic （ROC） analysis were performed in training set to find out risk factors ofintra-abdominal metastasis, and then validate it in testing set. Results： Out of 249 cM0 patients, 51 （20.5%） patients with intra-abdominal metastasis were identified by diagnostic laparoscopy, including 20 （8.0%） P1CY1, 17 （6.8%） POCY1 and 14 （5.6%） P1CY0 patients. In the training set, multivariate logistic regression analysis and ROC analysis showed that the depth of tumor invasion on computer tomography （CT） scan ≥21 mm and tumor-occupied 〉2 portions of stomach are predictive factors of metastasis. In the testing set, when diagnostic laparoscopy was performed on patients who had one or two of these risk factors, the sensitivity and positive predictive value for detecting intra-abdominal metastasis were 90.0% and 32.1%, respectively. Conclusions： According to our results, depth of tumor invasion and tumor-occupied portions of stomach are predictive factors ofintra-abdominal metastasis.展开更多
This paper presents a comprehensive area expansion prediction index method to apply GNSS for short-impending prediction of earthquakes. Based on continuous GNSS observation data from Yunnan Province, a displacement fi...This paper presents a comprehensive area expansion prediction index method to apply GNSS for short-impending prediction of earthquakes. Based on continuous GNSS observation data from Yunnan Province, a displacement field was detected after data cycle-slip repair using precision data processing software and geophysical field effect model correction. The Yunnan area was divided into 56 grid cells for displacement field interpolation to obtain a more uniform displacement field and a strain field variation time series. The pre-earthquake response of each grid-cell expansion time series was evaluated and synthesized to extract a short-impending earthquake anomaly identification index. The results show that this index indicated occurrence times and hypocenter for earthquakes of magnitude M≥5. Fourteen earthquakes were predicted accurately, and there were five false reports. This index can therefore be used for the short-impending prediction of earthquakes.展开更多
DNA-binding one zinc-finger(Dof)proteins constitute a family of transcription factors with a highly conserved Dof domain that contains a C2C2 zinc-finger motif.Although several studies have demonstrated that Dof prote...DNA-binding one zinc-finger(Dof)proteins constitute a family of transcription factors with a highly conserved Dof domain that contains a C2C2 zinc-finger motif.Although several studies have demonstrated that Dof proteins are involved in multiple plant processes,including development and stress resistance,the functions of these proteins in drought stress resistance are largely unknown.Here,we report the identification of the MdDof54 gene from apple and document its positive roles in apple drought resistance.After long-term drought stress,compared with nontransgenic plants,MdDof54 RNAi plants had significantly shorter heights and weaker root systems;the transgenic plants also had lower shoot and root hydraulic conductivity,as well as lower photosynthesis rates.By contrast,compared with nontransgenic plants,MdDof54-overexpressing plants had higher photosynthesis rates and shoot hydraulic conductivity under long-term drought stress.Moreover,compared with nontransgenic plants,MdDof54-overexpressing plants had higher survival percentages under short-term drought stress,whereas MdDof54 RNAi plants had lower survival percentages.MdDof54 RNAi plants showed significant downregulation of 99 genes and significant upregulation of 992 genes in response to drought,and 366 of these genes were responsive to drought.We used DAPseq and ChIP-seq analyses to demonstrate that MdDof54 recognizes cis-elements that contain an AAAG motif.Taken together,our results provide new information on the functions of MdDof54 in plant drought stress resistance as well as resources for apple breeding aimed at the improvement of drought resistance.展开更多
It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without...It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.展开更多
We carried out a downscaling treatment over China using the CarbonTracker numerical model,which was applied using double grid nesting technology(3°×2°over the whole globe,1°×1°over China)...We carried out a downscaling treatment over China using the CarbonTracker numerical model,which was applied using double grid nesting technology(3°×2°over the whole globe,1°×1°over China),simulating and analyzing atmospheric CO2concentrations over 10 recent years(2000–2009).The simulation results agreed very well with observed data from four background atmospheric monitoring stations in China(The periods for which the simulation results and observed values be compared were January2000 to December 2009 for the WLG station and June 2006 to December 2009 for the SDZ,LFS,and LAN stations),giving correlation coefficients of>0.7.The high-resolution simulation data correlated slightly better than the low resolution simulation data with the observed data for three of the regions’atmospheric background stations.Further analysis of the annual,seasonal CO2concentration variations at the background stations showed that the CO2concentration increased each year over the study period,with an average annual increase of more than 5%,and annual increases of more than 7%at the Shangdianzi and Lin’an stations.Seasonal CO2variations were greater at the Longfengshan station than at the Shangdianzi or Lin’an stations.However,the CO2concentrations were higher at the Shangdianzi and Lin’an stations because they are greatly affected by human activities in the Jingjinji and Changjiang Delta economic zones.Spatial distribution in CO2concentrations and fluxes were higher in eastern than in western China.展开更多
High temperature stress on different varieties of lettuce seedlings in MDA, proline and soluble sugar content were studied. The results were as follows : With the stress temperature, varieties of leaf lettuce seedling...High temperature stress on different varieties of lettuce seedlings in MDA, proline and soluble sugar content were studied. The results were as follows : With the stress temperature, varieties of leaf lettuce seedlings in the MDA, proline and soluble sugar content gradually increased;Different varieties had the most significant difference in 38/33℃(d/n). The increase of heat-resistant varieties on proline and soluble sugar content was quick and high, while its increase in MDA content was slow and small.展开更多
Three-dimensionally ordered macroporous(3DOM)perovskite materials have attracted the interest from researchers worldwide due to their unique macroporous structure,flexible composition,tailorable physicochemical proper...Three-dimensionally ordered macroporous(3DOM)perovskite materials have attracted the interest from researchers worldwide due to their unique macroporous structure,flexible composition,tailorable physicochemical property,high stability and biocompatibility.In particular,they were widely used in environmental field,such as photocatalysis,catalytic combustion,catalytic oxidation and sensors.In this review,the recent progresses in the synthesis of 3DOM perovskite materials and their environmental applications are summarized.The advantages and the promoting mechanisms of 3DOM perovskite materials for different applications are discussed in detail.Subsequently,the challenges and perspectives on the topic are proposed.展开更多
An ultrafast fiber laser system comprising two coherently combined amplifier channels is reported.Within this system,each channel incorporates a rod-type fiber power amplifier,with individual operations reaching appro...An ultrafast fiber laser system comprising two coherently combined amplifier channels is reported.Within this system,each channel incorporates a rod-type fiber power amplifier,with individual operations reaching approximately 233 W.The active-locking of these coherently combined channels,followed by compression using gratings,yields an output with a pulse energy of 504μJ and an average power of 403 W.Exceptional stability is maintained,with a 0.3%root mean square(RMS)deviation and a beam quality factor M^(2)<1.2.Notably,precise dispersion management of the front-end seed light effectively compensates for the accumulated high-order dispersion in subsequent amplification stages.This strategic approach results in a significant reduction in the final output pulse duration for the coherently combined laser beam,reducing it from 488 to 260 fs after the gratings compressor,while concurrently enhancing the energy of the primary peak from 65%to 92%.展开更多
Many uncertain factors in the excavation process may lead to excessive lateral displacement or overlimited internal force of the piles,as well as inordinate settlement of soil surrounding the existing bridge foundatio...Many uncertain factors in the excavation process may lead to excessive lateral displacement or overlimited internal force of the piles,as well as inordinate settlement of soil surrounding the existing bridge foundation.Safety control is pivotal to ensuring the safety of adjacent structures.In this paper,an innovative method is proposed that combines an analytic hierarchy process(AHP)with a finite element method(FEM)to reveal the potential impact risk of uncertain factors on the surrounding environment.The AHP was adopted to determine key influencing factors based on the weight of each influencing factor.The FEM was used to quantify the impact of the key influencing factors on the surrounding environment.In terms of the AHP,the index system of uncertain factors was established based on an engineering investigation.A matrix comparing the lower index layer to the upper index layer,and the weight of each influencing factor,were calculated.It was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental factors.For the FEM,the FE baseline model was calibrated based on the case of no bridge surrounding the foundation pit.The consistency between the monitoring data and the numerical simulation data for a ground settlement was analyzed.FE simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge foundation.Furthermore,the lateral displacement of the bridge pile foundation,the internal force of the piles,and the settlement of the soil surrounding the pile foundation were emphatically analyzed.The most hazardous construction condition was also determined.Finally,two safety control measures for increasing the numbers of support levels and the rooted depths of the enclosure structure were suggested.A novel method for combining AHP with FEM can be used to determine the key influencing aspects among many uncertain factors during a construction,which can provide some beneficial references for enginee展开更多
Impregnated graphite has attracted considerable attention and has been widely used as an ideal friction material in many fields.However,the influence of the friction temperature on its tribological properties has not ...Impregnated graphite has attracted considerable attention and has been widely used as an ideal friction material in many fields.However,the influence of the friction temperature on its tribological properties has not been clearly studied;furthermore,the evolution mechanism of transferred tribofilm is unknown.In this study,the tribological properties of impregnated graphite were investigated at different friction temperatures,and the evolution of the carbon-based tribofilm was also determined.The results revealed that the tribological properties significantly improved with an increase in friction temperature.The friction coefficient and wear depth of impregnated graphite reduced by 68%and 75%,respectively,at a high temperature of 160℃ compared with those of non-impregnated graphite.The significant properties of the impregnated graphite can be attributed to a transferred carbon-based tribofilm with an ordered structure induced by the friction temperature,which uniformly and stably adsorbs on friction interfaces.This study provides an important basis for designing graphite-based friction materials with improved properties suited for industrial applications.展开更多
The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based ...The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based on gel materials(with excellent conductivity,mechanical tunability,environmental adaptability,and biocompatibility)are considered an advanced approach for developing a new generation of flexible sensors.This review comprehensively summarizes the recent advances in gel-based TENGs for flexible sensors,covering their principles,properties,and applications.Based on the development requirements for flexible sensors,the working mechanism of gel-based TENGs and the characteristic advantages of gels are introduced.Design strategies for the performance optimization of hydrogel-,organogel-,and aerogel-based TENGs are systematically summarized.In addition,the applications of gel-based TENGs in human motion sensing,tactile sensing,health monitoring,environmental monitoring,human-machine interaction,and other related fields are summarized.Finally,the challenges of gel-based TENGs for flexible sensing are discussed,and feasible strategies are proposed to guide future research.展开更多
Objective:This study aims to verify the feasibility and efficacy of laparoscopic lower mediastinal lymphadenectomy for Siewert typeⅡ/Ⅲadenocarcinoma of esophagogastric junction(AEG).Setting:An exploratory,observatio...Objective:This study aims to verify the feasibility and efficacy of laparoscopic lower mediastinal lymphadenectomy for Siewert typeⅡ/Ⅲadenocarcinoma of esophagogastric junction(AEG).Setting:An exploratory,observational,prospective,cohort study will be carried out under the Idea,Development,Exploration,Assessment and Long-term Follow-up(IDEAL)framework(stage 2 b).Paritcipants:The study will recruit 1,036 patients with cases of locally advanced AEG(Siewert typeⅡ/Ⅲ,clinical stage cT2-4 aN0-3 M0),and 518 will be assigned to either the laparoscopy group or the open group.Interventions:Patients will receive lower mediastinal lymphadenectomy along with either total or proximal gastrectomy.Primary and secondary outcome measures:The primary endpoint is the number of lower mediastinal lymph nodes retrieved,and the secondary endpoints are the surgical safety and prognosis,including intraoperative and postoperative lower-mediastinal-lymphadenectomy-related morbidity and mortality,rate of rehospitalization,R0 resection rate,3-year local recurrence rate,and 3-year overall survival.Conclusions:The study will provide data for the guidance and development of surgical treatment strategies for AEG.Trial registration number:The study has been registered in ClinicalTrials.gov(No.NCT04443478).展开更多
The metal-support interaction is of critical importance to enhance the catalytic activity and selectivity.However,it is still challenging to construct an appropriate interaction starting from the catalyst fabrication ...The metal-support interaction is of critical importance to enhance the catalytic activity and selectivity.However,it is still challenging to construct an appropriate interaction starting from the catalyst fabrication and/or activation.We herein established low-temperature treatment of Ni^(2+)ions impregnated on ceria in reductive atmosphere and reduction-oxidation cycles as effective approachs to regulate the metal-support interaction and raise the catalytic performance in the CO_(2)methanation.The proposed construction approach yielded Ni/Ce O_(2)that displayed highly dispersed Ni nanoparticles in contact with Ce O_(2)(111)and(100)facet,higher density of surface oxygen vacancies and larger amounts of weak basic sites relative to the reference samples,which increased the capacity for H2 and CO_(2)adsorption/activation.The interaction resulted in appreciably(2-3 fold)higher activity in the CO_(2)methanation with maintaining almost full selectivity to CH4 and high stability.Coverage of Ni surface by Ce O_(2)-x thin layer as a typical structure of strong metal-support interaction resulting from high-temperature reduction,can be alleviated via reduction-oxidation cycles.We also demonstrate the activation treatment-determined metalsupport interaction effect can generally extend to(Ti O_(2)and Zr O_(2))supported Ni catalysts.展开更多
Objective： Infra-pyloric artery （IPA） is an important anatomical landmark in treatment of gastric cancer and is the key vessel for pylorus-preserving gastrectomy and subgroup of infra-pyloric lymph nodes. However, ...Objective： Infra-pyloric artery （IPA） is an important anatomical landmark in treatment of gastric cancer and is the key vessel for pylorus-preserving gastrectomy and subgroup of infra-pyloric lymph nodes. However, its anatomical variation is not thoroughly understood. Our study aimed to clarify the origination of the IPA. Methods： We did this prospective, multicenter, open-label, observational study at gastric surgery departments of 34 hospitals in China. Gastric cancer patients aged 18 years or older and scheduled to undergo elective total or distal gastrectomy were assigned. During the surgery, IPA dissecting and exposing the origination point with photographs or video clips were required. The primary outcome was the origination of the IPA. Analysis of variance, χ2 tests and Fisher＇s tests were used to analyze the differences between groups. The study is registered at Clinicaltrials.gov （No. NCT03071237）. Results： Between May 8 and July 31, 2017, 429 patients were assigned for the study, and 419 （97.7%） patients had the IPA dissected and recorded through photograph or video and were included in the primary outcome analysis. The median age was 62 years old, and 73.7% were male. Among the patients, 78.5% received laparoscopic surgery. Single IPA origination was identified in 398 （95.0%） patients, including gastroduodenal artery （GDA） in 154 （36.8%） patients, anterior superior pancreaticoduodenal artery （ASPDA） in 130 （31.0%） patients, and right gastroepiploic artery （RGEA） in 114 （27.2%） patients. Fifteen （3.6%） patients were identified with multiple IPA and 6 （1.4%） patients were identified as IPA absence. The differences in the distribution of surgical approach （P=0.003） and geographic area （P=0.030） were statistically significant. No difference was shown in sex, age, gastrectomy type, tumor location, and clinical T, N and M stage. Conclusions： Our study found that the IPA originates from GDA, ASPDA and RGEA in similar proportions. Laparoscopic 展开更多
Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in...Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in nonelectrical industries.In this study,NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) is greatly improved via Ce(SO_(4))_(2) modification.It has been originally demonstrated that Ce^(4+)-SO_(4)^(2−)pair sites play crucial roles in improving NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) catalysts.The strong interaction between V species and Ce sites of Ce^(4+)-SO_(4)^(2−)pairs triggers the reaction between NH_(4)^(+) species and gaseous NO via Eley-Rideal(E-R)reaction pathway.After K-poisoning,the SO_(4)^(2−)sites of Ce^(4+)-SO_(4)^(2−)pairs as protective sites strongly bond with K and thus maintain the high reaction efficiency via the E-R reaction pathway.This work demonstrates an effective strategy to enhance NO_(x) reduction against alkali poisoning over catalysts via constructing Ce^(4+)-SO_(4)^(2−)pair sites,contributing to developing alkali-resistant SCR catalysts for practical application in nonelectrical industries.展开更多
Previous studies have reached consensus that low velocity zones are widespread in the crust beneath Yunnan region. However, the relationships between the low velocity zones and large faults, earthquake distribution ar...Previous studies have reached consensus that low velocity zones are widespread in the crust beneath Yunnan region. However, the relationships between the low velocity zones and large faults, earthquake distribution are less investigated by available studies. By analyzing the seismic ambient noise recorded by Yunnan Seismic Networks and Tengchong volcano array, we construct a 3D crustal shear wave velocity model for the Yunnan region, which provides more details of the distribution of intra-crustal low velocity zones all over Yunnan. The distribution of low velocity zones shows different features at different depths. At shallow depths, the results are well correlated with near surface geological features. With increasing depth, the low velocity zones are gradually concentrated on the northern part of our study area, most likely reflecting variations in crustal thickness beneath the Yunnan region. The low velocity zones are truncated at depth by several large faults in Yunnan. It is interesting that most strong earthquakes（Ms≥5.0） occurred in Yunnan are distributed in low velocity zones or the transition zones between low and high velocity anomalies within the upper-to-middle crust. The crustal structure is composed of a brittle, seismically active upper-to-middle crust and a warm, aseismic lower crust.展开更多
The present work combines polypyrrole with cobalt molybdenum oxide using an in situ surface growth method to adjust impedance matching and explore the microwave absorption performance of the composite material.The com...The present work combines polypyrrole with cobalt molybdenum oxide using an in situ surface growth method to adjust impedance matching and explore the microwave absorption performance of the composite material.The complex dielectric constant and magnetic permeability of the samples are measured in the frequency range of 2 to 18 GHz using a vector network analyzer,and their reflection loss(RL)value is investigated.The results show that the obtained PPy/Co_(x)Mo_(y)O_(z)composite exhibits excellent absorption performance at 17.68 GHz under a matching thickness of 2.0 mm,with an RL_(min)of-46.02 dB and an effective absorption bandwidth of 4.08 GHz.The excellent absorption performance can be attributed to the combined effect of multion loss mechanisms,including conduction loss,interface polarization,dipole polarization and eddy current loss.展开更多
基金Supported by National Natural Science Foundation of China (Grant No. 40775078)National Non-profit Research Project to Serve the Public Interest (Grant No. GYHY200806026)International S & T Cooperation Program of MOST(Grant No. 2007DFA20650)
文摘Atmospheric carbon dioxide is an important kind of greenhouse gas which influences global temperature. Its concentration variation could indicate the distribution of human and natural activities in various regions. Through the non-dispersive infrared method, flask sampling of atmospheric CO2 concen- tration was measured weekly at four national background stations including Waliguan, Shangdianzi, Lin’an, and Longfengshan. Based on the data collected from September 2006 to August 2007, along with the Waliguan station’s experience on in situ observational data processing, the selection methods for sampling data through the atmospheric background CO2 concentration analysis were preliminarily discussed. On the basis of this result, the variation features of the four typical regions’ atmospheric background CO2 concentration was analyzed for the first time. The results show that the atmospheric CO2 concentration at Waliguan, Shangdianzi, Lin’an, and Longfengshan is 383.5, 385.9, 387.8, and 384.3 ppm, respectively. During the research period, CO2 concentration at the Waliguan station changed slightly. However, the CO2 concentration changed sharply at the Shangdianzi and the Lin’an stations due to the great influence of human activities in the Jingjinji and the Changjiang Delta economic zones, and changed regularly with seasons at Longfengshan station under dual influences of human activities and plant photosynthesis. The results from this study can lay the foundation for more profound studies on atmospheric CO2 concentration level of different areas in China, and could be used to improve the understanding of carbon source and sink distribution.
基金supported by the National Natural Science Foundation of China(Grant Nos.41405129&41375130)the National Key Research and Development of China(Grant No.2017YFC0209701)
文摘Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.
基金supported by the National Key Technologies R & D Program of China (No. 2006BAC02A12)the Key Technologies R & D Program of Tianjin, China (No.07ZCGYSH02000)the Natural Science Foundationof Tianjin, China (No. 08JCZDJC21400).
文摘Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char （APTC） for Rhodamine B （RhB）. Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics.
基金supported by grants supporting the research program of early diagnosis, standardized treatment and therapy effect evaluation of gastric cancer (No. D141100000414004) from Beijing Ministry of Science and Technology
文摘Objective： Diagnostic laparoscopy is recommended for the pretherapeutic staging of gastric cancer to detect any unexpected or unconfirmed intra-abdominal metastasis. The aim of this study was to evaluate the role and indications of diagnostic laparoscopy in the detection of intra-abdominal metastasis. Methods： Standard diagnostic laparoscopy with peritoneal cytology examination was performed prospectively on patients who were clinically diagnosed with primary local advanced gastric cancer （CT≥2M0）. We calculated the rate of intra-abdominal metastases identified by diagnostic laparoscopy, and examined the relationship between peritoneal dissemination （P） and cytology results （CY）. Split-sample method was applied to find clinical risk factors for intra-abdominal metastasis. Multivariate logistic regression analysis and receiver-operator characteristic （ROC） analysis were performed in training set to find out risk factors ofintra-abdominal metastasis, and then validate it in testing set. Results： Out of 249 cM0 patients, 51 （20.5%） patients with intra-abdominal metastasis were identified by diagnostic laparoscopy, including 20 （8.0%） P1CY1, 17 （6.8%） POCY1 and 14 （5.6%） P1CY0 patients. In the training set, multivariate logistic regression analysis and ROC analysis showed that the depth of tumor invasion on computer tomography （CT） scan ≥21 mm and tumor-occupied 〉2 portions of stomach are predictive factors of metastasis. In the testing set, when diagnostic laparoscopy was performed on patients who had one or two of these risk factors, the sensitivity and positive predictive value for detecting intra-abdominal metastasis were 90.0% and 32.1%, respectively. Conclusions： According to our results, depth of tumor invasion and tumor-occupied portions of stomach are predictive factors ofintra-abdominal metastasis.
基金supported by the National 973 Project of China (No. 2013CB733303)the National Natural Science Foundation of China (No. 41474093)+4 种基金the Key Natural Science Foundation of Hubei Province (No. 2014CFA110)the open fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education (No. 15-02-07)the China Earthquake Administration’s Earthquake Science and Technology Spark Program (No. XH15037SX)Special fund of earthquake science and technology of Yunnan Earthquake Agency (No. 2017ZX02)the Jiancheng Li Academician Workstation (No. 2015IC015)
文摘This paper presents a comprehensive area expansion prediction index method to apply GNSS for short-impending prediction of earthquakes. Based on continuous GNSS observation data from Yunnan Province, a displacement field was detected after data cycle-slip repair using precision data processing software and geophysical field effect model correction. The Yunnan area was divided into 56 grid cells for displacement field interpolation to obtain a more uniform displacement field and a strain field variation time series. The pre-earthquake response of each grid-cell expansion time series was evaluated and synthesized to extract a short-impending earthquake anomaly identification index. The results show that this index indicated occurrence times and hypocenter for earthquakes of magnitude M≥5. Fourteen earthquakes were predicted accurately, and there were five false reports. This index can therefore be used for the short-impending prediction of earthquakes.
基金supported by the National Natural Science Foundation of China(31572106 and 31622049).
文摘DNA-binding one zinc-finger(Dof)proteins constitute a family of transcription factors with a highly conserved Dof domain that contains a C2C2 zinc-finger motif.Although several studies have demonstrated that Dof proteins are involved in multiple plant processes,including development and stress resistance,the functions of these proteins in drought stress resistance are largely unknown.Here,we report the identification of the MdDof54 gene from apple and document its positive roles in apple drought resistance.After long-term drought stress,compared with nontransgenic plants,MdDof54 RNAi plants had significantly shorter heights and weaker root systems;the transgenic plants also had lower shoot and root hydraulic conductivity,as well as lower photosynthesis rates.By contrast,compared with nontransgenic plants,MdDof54-overexpressing plants had higher photosynthesis rates and shoot hydraulic conductivity under long-term drought stress.Moreover,compared with nontransgenic plants,MdDof54-overexpressing plants had higher survival percentages under short-term drought stress,whereas MdDof54 RNAi plants had lower survival percentages.MdDof54 RNAi plants showed significant downregulation of 99 genes and significant upregulation of 992 genes in response to drought,and 366 of these genes were responsive to drought.We used DAPseq and ChIP-seq analyses to demonstrate that MdDof54 recognizes cis-elements that contain an AAAG motif.Taken together,our results provide new information on the functions of MdDof54 in plant drought stress resistance as well as resources for apple breeding aimed at the improvement of drought resistance.
基金This work was supported by the National Natural Science Foundation of China(Nos.51673040 and 21978048)the Natural Science Foundation of Jiangsu Province(Nos.BK20171357 and BK20180366)+4 种基金Opening Project of Guangxi Key Laboratory of Clean Pulp&Papermaking and Pollution Control(No.GD201802-5)the Fundamental Research Funds for Central Universities(No.2242019k30042)Scientific Innovation Research Foundation of College Graduate in Jiangsu Province(No.KYCX19_0103)Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.1107047002)Fund Project for Transformation of Scientific and Technological Achievements of Jiangsu Province of China(No.BA2018045).
文摘It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.
基金supported by the National Basic Research Program of China (2010CB950601)the International S & T Cooperation Program MOST (2011DFA21090)the National Natural Science Foundation of China (41175116)
文摘We carried out a downscaling treatment over China using the CarbonTracker numerical model,which was applied using double grid nesting technology(3°×2°over the whole globe,1°×1°over China),simulating and analyzing atmospheric CO2concentrations over 10 recent years(2000–2009).The simulation results agreed very well with observed data from four background atmospheric monitoring stations in China(The periods for which the simulation results and observed values be compared were January2000 to December 2009 for the WLG station and June 2006 to December 2009 for the SDZ,LFS,and LAN stations),giving correlation coefficients of>0.7.The high-resolution simulation data correlated slightly better than the low resolution simulation data with the observed data for three of the regions’atmospheric background stations.Further analysis of the annual,seasonal CO2concentration variations at the background stations showed that the CO2concentration increased each year over the study period,with an average annual increase of more than 5%,and annual increases of more than 7%at the Shangdianzi and Lin’an stations.Seasonal CO2variations were greater at the Longfengshan station than at the Shangdianzi or Lin’an stations.However,the CO2concentrations were higher at the Shangdianzi and Lin’an stations because they are greatly affected by human activities in the Jingjinji and Changjiang Delta economic zones.Spatial distribution in CO2concentrations and fluxes were higher in eastern than in western China.
文摘High temperature stress on different varieties of lettuce seedlings in MDA, proline and soluble sugar content were studied. The results were as follows : With the stress temperature, varieties of leaf lettuce seedlings in the MDA, proline and soluble sugar content gradually increased;Different varieties had the most significant difference in 38/33℃(d/n). The increase of heat-resistant varieties on proline and soluble sugar content was quick and high, while its increase in MDA content was slow and small.
基金supported by the Tianjin Municipal Natural Science Foundation(17JCYBJC22600)the Fundamental Research Funds for the Central Universities~~
文摘Three-dimensionally ordered macroporous(3DOM)perovskite materials have attracted the interest from researchers worldwide due to their unique macroporous structure,flexible composition,tailorable physicochemical property,high stability and biocompatibility.In particular,they were widely used in environmental field,such as photocatalysis,catalytic combustion,catalytic oxidation and sensors.In this review,the recent progresses in the synthesis of 3DOM perovskite materials and their environmental applications are summarized.The advantages and the promoting mechanisms of 3DOM perovskite materials for different applications are discussed in detail.Subsequently,the challenges and perspectives on the topic are proposed.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.9215010612021004,and 11934006)the Innovation Project of Optics Valley Laboratory(No.OVL2021ZD001),the Major Program(JD)of Hubei Province(No.203BAA015)the Cross Research Support Program of Huazhong University of Science and Technology(No.2023JCYJ041).
文摘An ultrafast fiber laser system comprising two coherently combined amplifier channels is reported.Within this system,each channel incorporates a rod-type fiber power amplifier,with individual operations reaching approximately 233 W.The active-locking of these coherently combined channels,followed by compression using gratings,yields an output with a pulse energy of 504μJ and an average power of 403 W.Exceptional stability is maintained,with a 0.3%root mean square(RMS)deviation and a beam quality factor M^(2)<1.2.Notably,precise dispersion management of the front-end seed light effectively compensates for the accumulated high-order dispersion in subsequent amplification stages.This strategic approach results in a significant reduction in the final output pulse duration for the coherently combined laser beam,reducing it from 488 to 260 fs after the gratings compressor,while concurrently enhancing the energy of the primary peak from 65%to 92%.
基金The authors acknowledge the National Key Research and Development Program of China(No.2017YFC0805402)the Open Project of the State Key Laboratory of Disaster Reduction in Civil Engineering(No.SLDRCE17-01)+1 种基金the Incentive Fund for Overseas Visits of Doctoral Students of Tianjin University in 2019(070-0903077101)the China Scholarship Council(CSC,201906250153)for their financial support.
文摘Many uncertain factors in the excavation process may lead to excessive lateral displacement or overlimited internal force of the piles,as well as inordinate settlement of soil surrounding the existing bridge foundation.Safety control is pivotal to ensuring the safety of adjacent structures.In this paper,an innovative method is proposed that combines an analytic hierarchy process(AHP)with a finite element method(FEM)to reveal the potential impact risk of uncertain factors on the surrounding environment.The AHP was adopted to determine key influencing factors based on the weight of each influencing factor.The FEM was used to quantify the impact of the key influencing factors on the surrounding environment.In terms of the AHP,the index system of uncertain factors was established based on an engineering investigation.A matrix comparing the lower index layer to the upper index layer,and the weight of each influencing factor,were calculated.It was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental factors.For the FEM,the FE baseline model was calibrated based on the case of no bridge surrounding the foundation pit.The consistency between the monitoring data and the numerical simulation data for a ground settlement was analyzed.FE simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge foundation.Furthermore,the lateral displacement of the bridge pile foundation,the internal force of the piles,and the settlement of the soil surrounding the pile foundation were emphatically analyzed.The most hazardous construction condition was also determined.Finally,two safety control measures for increasing the numbers of support levels and the rooted depths of the enclosure structure were suggested.A novel method for combining AHP with FEM can be used to determine the key influencing aspects among many uncertain factors during a construction,which can provide some beneficial references for enginee
基金supported by the National Key R&D Program of China(No.2018YFB2000801)the National Natural Science Foundation of China(No.51905027)+1 种基金the Tribology Science Fund of State Key Laboratory of Tribology(No.SKLTKF18A02)the Fundamental Research Funds for the Central Universities(No.BUCTRC201908).
文摘Impregnated graphite has attracted considerable attention and has been widely used as an ideal friction material in many fields.However,the influence of the friction temperature on its tribological properties has not been clearly studied;furthermore,the evolution mechanism of transferred tribofilm is unknown.In this study,the tribological properties of impregnated graphite were investigated at different friction temperatures,and the evolution of the carbon-based tribofilm was also determined.The results revealed that the tribological properties significantly improved with an increase in friction temperature.The friction coefficient and wear depth of impregnated graphite reduced by 68%and 75%,respectively,at a high temperature of 160℃ compared with those of non-impregnated graphite.The significant properties of the impregnated graphite can be attributed to a transferred carbon-based tribofilm with an ordered structure induced by the friction temperature,which uniformly and stably adsorbs on friction interfaces.This study provides an important basis for designing graphite-based friction materials with improved properties suited for industrial applications.
基金supported by the National Natural Science Foundation of China(22068005,22278091)the Training Program for 1000 Backbone Teachers in Guangxi(2022).
文摘The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based on gel materials(with excellent conductivity,mechanical tunability,environmental adaptability,and biocompatibility)are considered an advanced approach for developing a new generation of flexible sensors.This review comprehensively summarizes the recent advances in gel-based TENGs for flexible sensors,covering their principles,properties,and applications.Based on the development requirements for flexible sensors,the working mechanism of gel-based TENGs and the characteristic advantages of gels are introduced.Design strategies for the performance optimization of hydrogel-,organogel-,and aerogel-based TENGs are systematically summarized.In addition,the applications of gel-based TENGs in human motion sensing,tactile sensing,health monitoring,environmental monitoring,human-machine interaction,and other related fields are summarized.Finally,the challenges of gel-based TENGs for flexible sensing are discussed,and feasible strategies are proposed to guide future research.
基金supported by the Chinese Medical Foundation(No.2020064)。
文摘Objective:This study aims to verify the feasibility and efficacy of laparoscopic lower mediastinal lymphadenectomy for Siewert typeⅡ/Ⅲadenocarcinoma of esophagogastric junction(AEG).Setting:An exploratory,observational,prospective,cohort study will be carried out under the Idea,Development,Exploration,Assessment and Long-term Follow-up(IDEAL)framework(stage 2 b).Paritcipants:The study will recruit 1,036 patients with cases of locally advanced AEG(Siewert typeⅡ/Ⅲ,clinical stage cT2-4 aN0-3 M0),and 518 will be assigned to either the laparoscopy group or the open group.Interventions:Patients will receive lower mediastinal lymphadenectomy along with either total or proximal gastrectomy.Primary and secondary outcome measures:The primary endpoint is the number of lower mediastinal lymph nodes retrieved,and the secondary endpoints are the surgical safety and prognosis,including intraoperative and postoperative lower-mediastinal-lymphadenectomy-related morbidity and mortality,rate of rehospitalization,R0 resection rate,3-year local recurrence rate,and 3-year overall survival.Conclusions:The study will provide data for the guidance and development of surgical treatment strategies for AEG.Trial registration number:The study has been registered in ClinicalTrials.gov(No.NCT04443478).
基金financially supported by the Tianjin Key Science and Technology Project(19ZXNCGX00030)。
文摘The metal-support interaction is of critical importance to enhance the catalytic activity and selectivity.However,it is still challenging to construct an appropriate interaction starting from the catalyst fabrication and/or activation.We herein established low-temperature treatment of Ni^(2+)ions impregnated on ceria in reductive atmosphere and reduction-oxidation cycles as effective approachs to regulate the metal-support interaction and raise the catalytic performance in the CO_(2)methanation.The proposed construction approach yielded Ni/Ce O_(2)that displayed highly dispersed Ni nanoparticles in contact with Ce O_(2)(111)and(100)facet,higher density of surface oxygen vacancies and larger amounts of weak basic sites relative to the reference samples,which increased the capacity for H2 and CO_(2)adsorption/activation.The interaction resulted in appreciably(2-3 fold)higher activity in the CO_(2)methanation with maintaining almost full selectivity to CH4 and high stability.Coverage of Ni surface by Ce O_(2)-x thin layer as a typical structure of strong metal-support interaction resulting from high-temperature reduction,can be alleviated via reduction-oxidation cycles.We also demonstrate the activation treatment-determined metalsupport interaction effect can generally extend to(Ti O_(2)and Zr O_(2))supported Ni catalysts.
基金funded by the Gastric Cancer Diagnose and Treatment Project(D171100006517004,D17110700650000)of Beijing Municipal Science&Technology Commissionsupported by Beijing Municipal Administration of Hospital Clinical Medicine Development of Special Funding Support(ZYLX201701)
文摘Objective： Infra-pyloric artery （IPA） is an important anatomical landmark in treatment of gastric cancer and is the key vessel for pylorus-preserving gastrectomy and subgroup of infra-pyloric lymph nodes. However, its anatomical variation is not thoroughly understood. Our study aimed to clarify the origination of the IPA. Methods： We did this prospective, multicenter, open-label, observational study at gastric surgery departments of 34 hospitals in China. Gastric cancer patients aged 18 years or older and scheduled to undergo elective total or distal gastrectomy were assigned. During the surgery, IPA dissecting and exposing the origination point with photographs or video clips were required. The primary outcome was the origination of the IPA. Analysis of variance, χ2 tests and Fisher＇s tests were used to analyze the differences between groups. The study is registered at Clinicaltrials.gov （No. NCT03071237）. Results： Between May 8 and July 31, 2017, 429 patients were assigned for the study, and 419 （97.7%） patients had the IPA dissected and recorded through photograph or video and were included in the primary outcome analysis. The median age was 62 years old, and 73.7% were male. Among the patients, 78.5% received laparoscopic surgery. Single IPA origination was identified in 398 （95.0%） patients, including gastroduodenal artery （GDA） in 154 （36.8%） patients, anterior superior pancreaticoduodenal artery （ASPDA） in 130 （31.0%） patients, and right gastroepiploic artery （RGEA） in 114 （27.2%） patients. Fifteen （3.6%） patients were identified with multiple IPA and 6 （1.4%） patients were identified as IPA absence. The differences in the distribution of surgical approach （P=0.003） and geographic area （P=0.030） were statistically significant. No difference was shown in sex, age, gastrectomy type, tumor location, and clinical T, N and M stage. Conclusions： Our study found that the IPA originates from GDA, ASPDA and RGEA in similar proportions. Laparoscopic
基金the National Natural Science Foundation of China(Nos.22125604,22106100,21976117)Shanghai Rising-Star Program(No.22QA1403700)+1 种基金Chenguang Program supported by Shanghai Education Development FoundationShanghai Municipal Education Commission(No.22Z00354).
文摘Commercial V_(2)O_(5)-based catalysts have been successfully applied in NH_(3) selective catalytic reduction(NH_(3)-SCR)of NO_(x) from power stations,but their poor alkali-resistance restrains the wider application in nonelectrical industries.In this study,NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) is greatly improved via Ce(SO_(4))_(2) modification.It has been originally demonstrated that Ce^(4+)-SO_(4)^(2−)pair sites play crucial roles in improving NO_(x) reduction against alkali poisoning over V_(2)O_(5)/TiO_(2) catalysts.The strong interaction between V species and Ce sites of Ce^(4+)-SO_(4)^(2−)pairs triggers the reaction between NH_(4)^(+) species and gaseous NO via Eley-Rideal(E-R)reaction pathway.After K-poisoning,the SO_(4)^(2−)sites of Ce^(4+)-SO_(4)^(2−)pairs as protective sites strongly bond with K and thus maintain the high reaction efficiency via the E-R reaction pathway.This work demonstrates an effective strategy to enhance NO_(x) reduction against alkali poisoning over catalysts via constructing Ce^(4+)-SO_(4)^(2−)pair sites,contributing to developing alkali-resistant SCR catalysts for practical application in nonelectrical industries.
基金financially supported by the National 973-Project(No.2013CB733303)the National Natural Science Foundation of China(No.41474093)the Key Natural Science Foundation of Hubei Province(No.2014CFA110)
文摘Previous studies have reached consensus that low velocity zones are widespread in the crust beneath Yunnan region. However, the relationships between the low velocity zones and large faults, earthquake distribution are less investigated by available studies. By analyzing the seismic ambient noise recorded by Yunnan Seismic Networks and Tengchong volcano array, we construct a 3D crustal shear wave velocity model for the Yunnan region, which provides more details of the distribution of intra-crustal low velocity zones all over Yunnan. The distribution of low velocity zones shows different features at different depths. At shallow depths, the results are well correlated with near surface geological features. With increasing depth, the low velocity zones are gradually concentrated on the northern part of our study area, most likely reflecting variations in crustal thickness beneath the Yunnan region. The low velocity zones are truncated at depth by several large faults in Yunnan. It is interesting that most strong earthquakes（Ms≥5.0） occurred in Yunnan are distributed in low velocity zones or the transition zones between low and high velocity anomalies within the upper-to-middle crust. The crustal structure is composed of a brittle, seismically active upper-to-middle crust and a warm, aseismic lower crust.
基金supported by the National Natural Science Foundation of China(22165032)
文摘The present work combines polypyrrole with cobalt molybdenum oxide using an in situ surface growth method to adjust impedance matching and explore the microwave absorption performance of the composite material.The complex dielectric constant and magnetic permeability of the samples are measured in the frequency range of 2 to 18 GHz using a vector network analyzer,and their reflection loss(RL)value is investigated.The results show that the obtained PPy/Co_(x)Mo_(y)O_(z)composite exhibits excellent absorption performance at 17.68 GHz under a matching thickness of 2.0 mm,with an RL_(min)of-46.02 dB and an effective absorption bandwidth of 4.08 GHz.The excellent absorption performance can be attributed to the combined effect of multion loss mechanisms,including conduction loss,interface polarization,dipole polarization and eddy current loss.
