check,check on 和 check up on 都包含“检查”、“核对”的意义。例如:1.checkI have checked your answers and none of them are correct.我检查了你的答案,没有一个正确。When I checked my shopping list I found I’d forgotten ...check,check on 和 check up on 都包含“检查”、“核对”的意义。例如:1.checkI have checked your answers and none of them are correct.我检查了你的答案,没有一个正确。When I checked my shopping list I found I’d forgotten to buy eggs.我核对购物单时发现忘记买蛋了。展开更多
You can use the word“check”in many ways.When you check into something,you find out more about it.When you check something out,you look at that thing carefully.To check out a place,you may actually go there.When you ...You can use the word“check”in many ways.When you check into something,you find out more about it.When you check something out,you look at that thing carefully.To check out a place,you may actually go there.When you check in on someone,you go to their place.You may ask,“How are you doing?”展开更多
Decentralized methods for targeting poverty are widely adopted in developing countries to improve the performance of various poverty alleviation programs.A common challenge for implementing successful decentralized ta...Decentralized methods for targeting poverty are widely adopted in developing countries to improve the performance of various poverty alleviation programs.A common challenge for implementing successful decentralized targeting is the existence of elite capture.China has recently implemented a nationwide decentralized poverty targeting program,the targeted poverty alleviation(TPA)policy,to achieve the national goal of eliminating absolute poverty by the end of 2020.As the largest decentralized poverty targeting program in the world,TPA's successful implementation was believed to be threatened by elite capture in some earlier reports.Since 2015,a targeting correction mechanism,called"follow-up checks"policy,has been introduced.With the"follow-up checks"policy,the elites and other ineligible households who receive benefits under TPA were removed from the program.This paper investigates the elite capture phenomenon in TPA using village census data from a poverty-stricken county in 2017-two years after implementing the"follow-up checks"policy.We find no evidence of elite capture in TPA.The elites are unlikely to become beneficiaries or receive more benefits than non-elites.Our results contradict earlier findings that reported elite capture in TPA.We argue that the reason is the accountability emphasized by the central government in the"follow-up checks"policy.Our findings imply that having proper accountability is critical for improving targeting performance by global antipoverty initiatives.展开更多
The present study aims to determine the gynecologic health status of asymptomatic women at a unique Japanese Health Check-up Institute, Ningen Dock. Medical records of Japanese women, who underwent gynecological medic...The present study aims to determine the gynecologic health status of asymptomatic women at a unique Japanese Health Check-up Institute, Ningen Dock. Medical records of Japanese women, who underwent gynecological medical (health) examinations between January 2011 and December 2016, were retrospectively reviewed. Of the cervical smears from 8927 women aged 18 - 85 years, 50 (0.6%) were classified as dysplastic and malignant changes: 18 of low-grade squamous intraepithelial lesion, 10 high-grade squamous intraepithelial lesion, 21 atypical squamous cells of undetermined significance and 1 cervical squamous cell carcinoma. No case of cervical adenocarcinoma was found. Ultrasonographic examination detected uterus enlargements and ovary tumors in 2.0% and 0.9% of cases, respectively. Most of participants (95.6%) revealed no gynecologic abnormalities. The present study based on the records of Ningen Dock, where asymptomatic participants undergo a medical examination at their own expense, showed very low incidence of abnormal cytologic and/or ultrasonographic findings.展开更多
Objective: In Japan, there are unique facilities (namely Ningen Dock) of health check-up, where asymptomatic participants undergo a medical examination at their own expense. The earlier occurrence of cervical cancer a...Objective: In Japan, there are unique facilities (namely Ningen Dock) of health check-up, where asymptomatic participants undergo a medical examination at their own expense. The earlier occurrence of cervical cancer and the concern on screening prompted us compare to the age distribution in the self-covered system with that of free physical check-up programs at public expense. Methods: We analyzed medical records of Japanese women, who underwent gynecological examinations at self-covered expense and at public expense between for the periods 2002-2011 and 2005-2009, respectively, restricting examinee’s age group. Results: For self-covered system, approximately 80% of the overall examinee population was occupied with three age groups 30-39, 40-49 and 50-59. The participants was extremely fewer in the over 60 years age group accounting for 10%, compared to those for the public expense-covered system, the over 60 years age group being 25%. Participant under the age of 30 years seemed to increase in chronological order in both systems. Conclusion: The level of knowledge on sexually transmitted infections may contribute to screening promotion for the younger women, while the elderly over 60 years’ attitudes toward screening may be mainly related to social-economic status and/or public expense support.展开更多
In this paper the application of spatialization technology on metadata quality check and updating was dis-cussed. A new method based on spatialization was proposed for checking and updating metadata to overcome the de...In this paper the application of spatialization technology on metadata quality check and updating was dis-cussed. A new method based on spatialization was proposed for checking and updating metadata to overcome the defi-ciency of text based methods with the powerful functions of spatial query and analysis provided by GIS software. Thismethod employs the technology of spatialization to transform metadata into a coordinate space and the functions ofspatial analysis in GIS to check and update spatial metadata in a visual environment. The basic principle and technicalflow of this method were explained in detail, and an example of implementation using ArcMap of GIS software wasillustrated with a metadata set of digital raster maps. The result shows the new method with the support of interactionof graph and text is much more intuitive and convenient than the ordinary text based method, and can fully utilize thefunctions of GIS spatial query and analysis with more accuracy and efficiency.展开更多
This paper describes the present condition of credit checking industry and the market of Chinese,elaborates what has restricted Chinese credit development,presents the possible credit products of current Chinese credi...This paper describes the present condition of credit checking industry and the market of Chinese,elaborates what has restricted Chinese credit development,presents the possible credit products of current Chinese credit checking market,forecasts the profits of credit checking service in China,and indicates the strategic steps of operation on credit checking service in China."Credit"is one of the most popular words in the last two years in China,every thing related to credit will heat up,and the credit management is also becoming a burgeoning industry and comes to front.The development of economy has called for construction of the social credit system,which brings great business opportunities to the credit management agency.Therefore,the government,the industry and the private focus on this wealth dinner.Once deeming it as a great opportunity some far-sighted men bravely begin to take tough practice in the huge market.From then on,some credit management companies have come into being a part of the credit checking agent industry.展开更多
<strong><em>Background</em></strong> A serum uric acid (UA) level of 7.0 mg/dL has been used as the criterion for hyperuricemia in Japan regardless of gender, despite higher serum UA levels in ...<strong><em>Background</em></strong> A serum uric acid (UA) level of 7.0 mg/dL has been used as the criterion for hyperuricemia in Japan regardless of gender, despite higher serum UA levels in men than in women. Serum UA has been identified as a predictive biomarker for metabolic syndrome (MetS);however, the gender differences in the association between UA levels and MetS-related conditions in a Japanese population have not been completely assessed. <strong><em>Objective</em></strong> To examine gender and age differences in the associations between serum UA levels and other biomarkers within a health-screened Japanese population and to evaluate the usefulness of serum UA as a predictor of MetS between the two genders. <strong><em>Methods</em></strong> A cross-sectional study of healthy individuals in Japan (16,391 men;16,656 women) was conducted. Associations between UA and several biomarkers were analyzed for each gender type and for age- and serum UA level-stratified groups. Logistic regression was used to analyze the association of age and serum UA levels with MetS-related conditions. Receiver operating characteristic (ROC) curve analysis was performed to identify the UA cut-off value for predicting the risk of the MetS-related conditions. <strong><em>Results</em></strong> Serum UA levels in women had stronger correlations with MetS-related biomarkers than in men. After adjusting for age, the odds ratios for a 1-mg/dL serum UA increase for diabetes mellitus and dyslipidemia in women were 1.13 (95% confidence interval, 1.04 - 1.23) and 1.30 (1.25 - 1.34), respectively. In ROC analysis, women had significantly higher area under the curve (AUC) values for MetS prediction than men. <em><strong>Conclusion</strong></em> An elevated serum UA level has a higher predictive ability for the risk of MetS-related conditions in Japanese women than in men. The optimal serum UA cut-off value for MetS in women was suggested to be approximately 5 mg/dL, remarkably lower than that in men.展开更多
The tokamak HT-7U project has been funded as a Chinese national project since 1998. The main object of the project is to build a nuclear fusion experimental device with divertor configuration, which is designed by the...The tokamak HT-7U project has been funded as a Chinese national project since 1998. The main object of the project is to build a nuclear fusion experimental device with divertor configuration, which is designed by the Institute of Plasma Physics, the Chinese Academy of Sciences (ASIPP). It is a full superconducting device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coil. During the operation of the device, the operational parameter of device should be checked by technical diagnosis. This paper describes the design of circuit for checldng short between every two parts of the HT7U device. The main contents of design include circuit of data acquisition and data processing of computer.展开更多
Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environment...Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.展开更多
BACKGROUND Bacterial contamination during colonoscopy is a significant concern,yet few studies have evaluated bacterial aerosols.This study aimed to determine whether covering the biopsy hole check valve with enzymoly...BACKGROUND Bacterial contamination during colonoscopy is a significant concern,yet few studies have evaluated bacterial aerosols.This study aimed to determine whether covering the biopsy hole check valve with enzymolysis gauze(refers to sterile gauze soaked in a multi-enzyme cleaning solution)reduces bacterial air pollution in endoscopy rooms.AIM To evaluate the efficacy of an enzymolysis gauze cover in reducing bacterial aerosols from the biopsy valve.METHODS This prospective,single-blind trial included 80 patients undergoing elective diagnostic colonoscopy.During the procedure,the biopsy hole check valve was either covered or left uncovered with enzymolysis gauze.Air samples(100 L)were collected at a distance of 30 cm from the biopsy hole check valve and approximately 140 cm above the floor using a percussive air sampling instrument.Gram-positive bacteria were cultured on standard 90 mm colimycin nalidixic agar blood plates.The primary outcome measures were bacterial load and species identification.RESULTS Covering the biopsy hole check valve with enzymolysis gauze reduced bacterial load near the check valve from 50 colony-forming unit(CFU)/m^(3)[interquartile range(IQR):30-80]to 20 CFU/m^(3)(IQR:10-20).At the end of the procedure each day,covering the valve also decreased bacterial load in the endoscopy room from 35 CFU/m^(3)(IQR:33-85)to 10 CFU/m^(3)(IQR:5-10).The predominant bacteria identified were Gram-positive cocci.CONCLUSION Applying enzymolysis gauze to cover the biopsy hole check valve significantly reduces bacterial aerosol contamination in endoscopy rooms during colonoscopy.展开更多
The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-...The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-debris flow events, it is imperative to quantitatively assess the volume of sediment volume captured by the cascade check dams and to monitor their impact on sediment dynamics. This study investigates the cascade check dams in Guanmenzi Gully, Beichuan County, Sichuan Province in Southwest China, surveying the reservoir topography of the dams on two occasions over a fiveyear period. The #3 closed-type dam, located in the upper upstream, the #2 closed-type dam, located in the middle stream(which was manually cleaned), and the beam dam, located in the downstream were all surveyed. A simplified yet accurate method was developed to estimate sediment volume within check dam reservoirs under complex topographic conditions. A combination of terrestrial surveys and Unmanned Aerial Vehicle(UAV) based surveys was employed, resulting in the acquisition of two high-resolution Digital Elevation Models(DEMs) at different temporal intervals. The utilization of DEMs of Difference(DoD) facilitated the quantification of terrain variations and the sediment transport. The following conclusions were obtained: firstly, it was found that the volume of sediment trapped in the reservoirs of #2 closed-type dam and #1 beam dam were almost the same, with #3 closed-type dam being the smallest. The validation of the results in conjunction with the geometric method demonstrated that the percentage error was less than 7%, proving the reliability of the results. In addition, an analysis of changes in the detailed topography of the reservoirs revealed that the sediment deposit occurred in areas distant from the structures, while erosion exhibited concentration in specific areas close to the dams. The percentage volume of sediment deposit was found to be significantly higher than that of erosion(all higher than 85%). Furthermore, the excessive sediment deposition reduces the storage capacity of closed-type check dams, whereas in the case of beam dams, the maximum erosion amount in the reservoir is 35.8 m^(3) and the percentage of the maximum erosion amount is 14.00%. This suggests that the self-cleaning of beam dam can effectively slow down the sediment deposition process. Finally, the current study proposes an expression for storage capacity composition and suggests that, in engineering practice, emphasis should be placed on maintenance programs that synergize manual cleaning and self-cleaning of open-type check dams. The conclusions may facilitate the refinement of maintenance strategies of cascade check dams, thereby effectively preventing and mitigating debris flows.展开更多
文摘check,check on 和 check up on 都包含“检查”、“核对”的意义。例如:1.checkI have checked your answers and none of them are correct.我检查了你的答案,没有一个正确。When I checked my shopping list I found I’d forgotten to buy eggs.我核对购物单时发现忘记买蛋了。
文摘You can use the word“check”in many ways.When you check into something,you find out more about it.When you check something out,you look at that thing carefully.To check out a place,you may actually go there.When you check in on someone,you go to their place.You may ask,“How are you doing?”
基金supported by the National Natural Science Foundation of China(71661147001 and 71603228)the China Postdoctoral Science Foundation(2018M630687 and 2018T110607)the Zhejiang University-IFPRI Center for International Development Studies。
文摘Decentralized methods for targeting poverty are widely adopted in developing countries to improve the performance of various poverty alleviation programs.A common challenge for implementing successful decentralized targeting is the existence of elite capture.China has recently implemented a nationwide decentralized poverty targeting program,the targeted poverty alleviation(TPA)policy,to achieve the national goal of eliminating absolute poverty by the end of 2020.As the largest decentralized poverty targeting program in the world,TPA's successful implementation was believed to be threatened by elite capture in some earlier reports.Since 2015,a targeting correction mechanism,called"follow-up checks"policy,has been introduced.With the"follow-up checks"policy,the elites and other ineligible households who receive benefits under TPA were removed from the program.This paper investigates the elite capture phenomenon in TPA using village census data from a poverty-stricken county in 2017-two years after implementing the"follow-up checks"policy.We find no evidence of elite capture in TPA.The elites are unlikely to become beneficiaries or receive more benefits than non-elites.Our results contradict earlier findings that reported elite capture in TPA.We argue that the reason is the accountability emphasized by the central government in the"follow-up checks"policy.Our findings imply that having proper accountability is critical for improving targeting performance by global antipoverty initiatives.
文摘The present study aims to determine the gynecologic health status of asymptomatic women at a unique Japanese Health Check-up Institute, Ningen Dock. Medical records of Japanese women, who underwent gynecological medical (health) examinations between January 2011 and December 2016, were retrospectively reviewed. Of the cervical smears from 8927 women aged 18 - 85 years, 50 (0.6%) were classified as dysplastic and malignant changes: 18 of low-grade squamous intraepithelial lesion, 10 high-grade squamous intraepithelial lesion, 21 atypical squamous cells of undetermined significance and 1 cervical squamous cell carcinoma. No case of cervical adenocarcinoma was found. Ultrasonographic examination detected uterus enlargements and ovary tumors in 2.0% and 0.9% of cases, respectively. Most of participants (95.6%) revealed no gynecologic abnormalities. The present study based on the records of Ningen Dock, where asymptomatic participants undergo a medical examination at their own expense, showed very low incidence of abnormal cytologic and/or ultrasonographic findings.
文摘Objective: In Japan, there are unique facilities (namely Ningen Dock) of health check-up, where asymptomatic participants undergo a medical examination at their own expense. The earlier occurrence of cervical cancer and the concern on screening prompted us compare to the age distribution in the self-covered system with that of free physical check-up programs at public expense. Methods: We analyzed medical records of Japanese women, who underwent gynecological examinations at self-covered expense and at public expense between for the periods 2002-2011 and 2005-2009, respectively, restricting examinee’s age group. Results: For self-covered system, approximately 80% of the overall examinee population was occupied with three age groups 30-39, 40-49 and 50-59. The participants was extremely fewer in the over 60 years age group accounting for 10%, compared to those for the public expense-covered system, the over 60 years age group being 25%. Participant under the age of 30 years seemed to increase in chronological order in both systems. Conclusion: The level of knowledge on sexually transmitted infections may contribute to screening promotion for the younger women, while the elderly over 60 years’ attitudes toward screening may be mainly related to social-economic status and/or public expense support.
基金Project 40301042 supported by Natural Science Foundation of China
文摘In this paper the application of spatialization technology on metadata quality check and updating was dis-cussed. A new method based on spatialization was proposed for checking and updating metadata to overcome the defi-ciency of text based methods with the powerful functions of spatial query and analysis provided by GIS software. Thismethod employs the technology of spatialization to transform metadata into a coordinate space and the functions ofspatial analysis in GIS to check and update spatial metadata in a visual environment. The basic principle and technicalflow of this method were explained in detail, and an example of implementation using ArcMap of GIS software wasillustrated with a metadata set of digital raster maps. The result shows the new method with the support of interactionof graph and text is much more intuitive and convenient than the ordinary text based method, and can fully utilize thefunctions of GIS spatial query and analysis with more accuracy and efficiency.
文摘This paper describes the present condition of credit checking industry and the market of Chinese,elaborates what has restricted Chinese credit development,presents the possible credit products of current Chinese credit checking market,forecasts the profits of credit checking service in China,and indicates the strategic steps of operation on credit checking service in China."Credit"is one of the most popular words in the last two years in China,every thing related to credit will heat up,and the credit management is also becoming a burgeoning industry and comes to front.The development of economy has called for construction of the social credit system,which brings great business opportunities to the credit management agency.Therefore,the government,the industry and the private focus on this wealth dinner.Once deeming it as a great opportunity some far-sighted men bravely begin to take tough practice in the huge market.From then on,some credit management companies have come into being a part of the credit checking agent industry.
文摘<strong><em>Background</em></strong> A serum uric acid (UA) level of 7.0 mg/dL has been used as the criterion for hyperuricemia in Japan regardless of gender, despite higher serum UA levels in men than in women. Serum UA has been identified as a predictive biomarker for metabolic syndrome (MetS);however, the gender differences in the association between UA levels and MetS-related conditions in a Japanese population have not been completely assessed. <strong><em>Objective</em></strong> To examine gender and age differences in the associations between serum UA levels and other biomarkers within a health-screened Japanese population and to evaluate the usefulness of serum UA as a predictor of MetS between the two genders. <strong><em>Methods</em></strong> A cross-sectional study of healthy individuals in Japan (16,391 men;16,656 women) was conducted. Associations between UA and several biomarkers were analyzed for each gender type and for age- and serum UA level-stratified groups. Logistic regression was used to analyze the association of age and serum UA levels with MetS-related conditions. Receiver operating characteristic (ROC) curve analysis was performed to identify the UA cut-off value for predicting the risk of the MetS-related conditions. <strong><em>Results</em></strong> Serum UA levels in women had stronger correlations with MetS-related biomarkers than in men. After adjusting for age, the odds ratios for a 1-mg/dL serum UA increase for diabetes mellitus and dyslipidemia in women were 1.13 (95% confidence interval, 1.04 - 1.23) and 1.30 (1.25 - 1.34), respectively. In ROC analysis, women had significantly higher area under the curve (AUC) values for MetS prediction than men. <em><strong>Conclusion</strong></em> An elevated serum UA level has a higher predictive ability for the risk of MetS-related conditions in Japanese women than in men. The optimal serum UA cut-off value for MetS in women was suggested to be approximately 5 mg/dL, remarkably lower than that in men.
文摘The tokamak HT-7U project has been funded as a Chinese national project since 1998. The main object of the project is to build a nuclear fusion experimental device with divertor configuration, which is designed by the Institute of Plasma Physics, the Chinese Academy of Sciences (ASIPP). It is a full superconducting device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coil. During the operation of the device, the operational parameter of device should be checked by technical diagnosis. This paper describes the design of circuit for checldng short between every two parts of the HT7U device. The main contents of design include circuit of data acquisition and data processing of computer.
基金National Natural Science Foundation of China,Grant/Award Number:42330719National Natural Science Foundation of China,Grant/Award Number:U2443228+1 种基金Power Construction Corporation of China,Grant/Award Number:DJ-ZDXM-2021-51China Institute of Water Resources and Hydropower Research,Grant/Award Number:GE121003A0042022。
文摘Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.
基金Supported by the Construction Fund of Key Medical Disciplines of Hangzhou,No.2025HZGF05the Key R and D Program of Zhejiang Province,No.2023C03054 and No.2024C03048+1 种基金the Key Discipline of Integrated Chinese and Western Medicine(Digestive Diseases)in Zhejiang Province,No.2024-XK-61the Zhejiang Province Medical and Health Science and Technology Plan Project,No.2021KY848.
文摘BACKGROUND Bacterial contamination during colonoscopy is a significant concern,yet few studies have evaluated bacterial aerosols.This study aimed to determine whether covering the biopsy hole check valve with enzymolysis gauze(refers to sterile gauze soaked in a multi-enzyme cleaning solution)reduces bacterial air pollution in endoscopy rooms.AIM To evaluate the efficacy of an enzymolysis gauze cover in reducing bacterial aerosols from the biopsy valve.METHODS This prospective,single-blind trial included 80 patients undergoing elective diagnostic colonoscopy.During the procedure,the biopsy hole check valve was either covered or left uncovered with enzymolysis gauze.Air samples(100 L)were collected at a distance of 30 cm from the biopsy hole check valve and approximately 140 cm above the floor using a percussive air sampling instrument.Gram-positive bacteria were cultured on standard 90 mm colimycin nalidixic agar blood plates.The primary outcome measures were bacterial load and species identification.RESULTS Covering the biopsy hole check valve with enzymolysis gauze reduced bacterial load near the check valve from 50 colony-forming unit(CFU)/m^(3)[interquartile range(IQR):30-80]to 20 CFU/m^(3)(IQR:10-20).At the end of the procedure each day,covering the valve also decreased bacterial load in the endoscopy room from 35 CFU/m^(3)(IQR:33-85)to 10 CFU/m^(3)(IQR:5-10).The predominant bacteria identified were Gram-positive cocci.CONCLUSION Applying enzymolysis gauze to cover the biopsy hole check valve significantly reduces bacterial aerosol contamination in endoscopy rooms during colonoscopy.
基金jointly funded by the National Key R&D Program of China (2024YFC3012705)the CAS Light of West China Program (Grant Recipient:Wanyu Zhao)+1 种基金the National Natural Science Foundation of China (Grant No.42201095)the Postdoctoral Research Project Special Funding of Sichuan (Grant No.TB2023028)。
文摘The implementation of the cascade check dam system, which integrates beam and closed-type dams, has been extensively adopted as a pivotal engineering measure for mitigating debris flow in Southwest China. In the post-debris flow events, it is imperative to quantitatively assess the volume of sediment volume captured by the cascade check dams and to monitor their impact on sediment dynamics. This study investigates the cascade check dams in Guanmenzi Gully, Beichuan County, Sichuan Province in Southwest China, surveying the reservoir topography of the dams on two occasions over a fiveyear period. The #3 closed-type dam, located in the upper upstream, the #2 closed-type dam, located in the middle stream(which was manually cleaned), and the beam dam, located in the downstream were all surveyed. A simplified yet accurate method was developed to estimate sediment volume within check dam reservoirs under complex topographic conditions. A combination of terrestrial surveys and Unmanned Aerial Vehicle(UAV) based surveys was employed, resulting in the acquisition of two high-resolution Digital Elevation Models(DEMs) at different temporal intervals. The utilization of DEMs of Difference(DoD) facilitated the quantification of terrain variations and the sediment transport. The following conclusions were obtained: firstly, it was found that the volume of sediment trapped in the reservoirs of #2 closed-type dam and #1 beam dam were almost the same, with #3 closed-type dam being the smallest. The validation of the results in conjunction with the geometric method demonstrated that the percentage error was less than 7%, proving the reliability of the results. In addition, an analysis of changes in the detailed topography of the reservoirs revealed that the sediment deposit occurred in areas distant from the structures, while erosion exhibited concentration in specific areas close to the dams. The percentage volume of sediment deposit was found to be significantly higher than that of erosion(all higher than 85%). Furthermore, the excessive sediment deposition reduces the storage capacity of closed-type check dams, whereas in the case of beam dams, the maximum erosion amount in the reservoir is 35.8 m^(3) and the percentage of the maximum erosion amount is 14.00%. This suggests that the self-cleaning of beam dam can effectively slow down the sediment deposition process. Finally, the current study proposes an expression for storage capacity composition and suggests that, in engineering practice, emphasis should be placed on maintenance programs that synergize manual cleaning and self-cleaning of open-type check dams. The conclusions may facilitate the refinement of maintenance strategies of cascade check dams, thereby effectively preventing and mitigating debris flows.
