A new classification algorithm for web mining is proposed on the basis of general classification algorithm for data mining in order to implement personalized information services. The building tree method of detecting...A new classification algorithm for web mining is proposed on the basis of general classification algorithm for data mining in order to implement personalized information services. The building tree method of detecting class threshold is used for construction of decision tree according to the concept of user expectation so as to find classification rules in different layers. Compared with the traditional C4.5 algorithm, the disadvantage of excessive adaptation in C4.5 has been improved so that classification results not only have much higher accuracy but also statistic meaning.展开更多
The paper contains a summary of some results of original research total aggregates. The main idea is determining the boundaries of the groups for classification of fuzzy and threshold aggregates using the method of de...The paper contains a summary of some results of original research total aggregates. The main idea is determining the boundaries of the groups for classification of fuzzy and threshold aggregates using the method of decomposing a mixture of probability distributions. The article presents the experience of partitions of a real aggregate as a finite mixture of probability distributions on private aggregates. Threshold value defined by the boundaries of private aggregates, will match the value of the phenomenon at the intersection of the curves of probability distributions, which extracted from the mixture. The proposed scheme of identification threshold aggregates has found practical application in the research of aggregate of Russian employees by level of payroll and establishing the optimal minimum value monthly wage. The official data of the Federal State Statistics Service were used.展开更多
In order to assess the climatical and ecological effect which returned the farmland to pasture or forest, the vegetation and crop in Northwest China with suitable threshold value were classified in this experiment by ...In order to assess the climatical and ecological effect which returned the farmland to pasture or forest, the vegetation and crop in Northwest China with suitable threshold value were classified in this experiment by using multi-temporal SPOT/VEGETATION dada and combing supervised classification with unsupervised classification. Compared with the data from Statistical Department and actual investigation, the precision of the classified result was above 85%.展开更多
Penile hypersensitivity plays an important role in premature ejaculation （PE）, but differences in penile sensitivity among subtypes of PE are unknown. Therefore, we compared penile sensory thresholds in PE subtypes ...Penile hypersensitivity plays an important role in premature ejaculation （PE）, but differences in penile sensitivity among subtypes of PE are unknown. Therefore, we compared penile sensory thresholds in PE subtypes of lifelong and acquired PE, PE with and without erectile dysfunction （ED）, PE with an intravaginal ejaculation latency time 〈1 min and 〉1 min, and PE with and without orgasmic pleasure perceptual dysfunction. During August 2014 to January 2016, 136 patients with PE were included. Penile warm, cold, and vibratory thresholds were measured. Data of clinical characteristics, sexual life, Premature Ejaculation Diagnostic Tool （PEDT） score, and the 5-item version of the International Index of Erectile Function （IIEF-5） score were collected. Vibratory thresholds of the PE with ED group were higher in the right coronal sulcus （median amplitude： 4.92 vs 3.65 μm, P= 0.02） and the right penile shaft （median amplitude： 3.87 vs 3.30 μm, P = 0.03）, while differences in penile sensory thresholds between other subtypes were not significant. The median PEDT score was lower in the PE without ED group （12 vs 14, P 〈 0.001）. The IIEF-5 and PEDT scores were negatively correlated （r = -0.29, P 〈 0.001）. Patients with orgasmic pleasure perceptual dysfunction had a lower median IIEF-5 score （20 vs 21, P = 0.02）. Patients with PE and ED had lower penile sensitivity, and ED was associated with more severe symptoms and weaker orgasmic pleasure perception. In men with PE, management of comorbid ED is necessary. In case of side effects in erectile function, topical anesthetics should be cautiously used in men with PE and ED.展开更多
In order to improve the accuracy of building structure identification using remote sensing images,a building structure classification method based on multi-feature fusion of UAV remote sensing image is proposed in thi...In order to improve the accuracy of building structure identification using remote sensing images,a building structure classification method based on multi-feature fusion of UAV remote sensing image is proposed in this paper.Three identification approaches of remote sensing images are integrated in this method:object-oriented,texture feature,and digital elevation based on DSM and DEM.So RGB threshold classification method is used to classify the identification results.The accuracy of building structure classification based on each feature and the multi-feature fusion are compared and analyzed.The results show that the building structure classification method is feasible and can accurately identify the structures in large-area remote sensing images.展开更多
In this work, we propose an original approach of semi-vectorial hybrid morphological segmentation for multicomponent images or multidimensional data by analyzing compact multidimensional histograms based on different ...In this work, we propose an original approach of semi-vectorial hybrid morphological segmentation for multicomponent images or multidimensional data by analyzing compact multidimensional histograms based on different orders. Its principle consists first of segment marginally each component of the multicomponent image into different numbers of classes fixed at K. The segmentation of each component of the image uses a scalar segmentation strategy by histogram analysis;we mainly count the methods by searching for peaks or modes of the histogram and those based on a multi-thresholding of the histogram. It is the latter that we have used in this paper, it relies particularly on the multi-thresholding method of OTSU. Then, in the case where i) each component of the image admits exactly K classes, K vector thresholds are constructed by an optimal pairing of which each component of the vector thresholds are those resulting from the marginal segmentations. In addition, the multidimensional compact histogram of the multicomponent image is computed and the attribute tuples or ‘colors’ of the histogram are ordered relative to the threshold vectors to produce (K + 1) intervals in the partial order giving rise to a segmentation of the multidimensional histogram into K classes. The remaining colors of the histogram are assigned to the closest class relative to their center of gravity. ii) In the contrary case, a vectorial spatial matching between the classes of the scalar components of the image is produced to obtain an over-segmentation, then an interclass fusion is performed to obtain a maximum of K classes. Indeed, the relevance of our segmentation method has been highlighted in relation to other methods, such as K-means, using unsupervised and supervised quantitative segmentation evaluation criteria. So the robustness of our method relatively to noise has been tested.展开更多
The South Aral Seabed is an extreme dryland ecosystem undergoing rapid transformation yet remains misrepresented or absent in global land cover datasets.Conventional vegetation indices,specifically the Normalized Diff...The South Aral Seabed is an extreme dryland ecosystem undergoing rapid transformation yet remains misrepresented or absent in global land cover datasets.Conventional vegetation indices,specifically the Normalized Difference Vegetation Index(NDVI),perform poorly in such environments due to their limited ability to distinguish sparse vegetation from highly reflective saline and sandy soils.This study evaluated the effectiveness of the Modified Soil Adjusted Vegetation Index(MSAVI)for improving land cover classification in the South Aral Seabed and conducted a decadal analysis of land cover change between 2013 and 2023 using Landsat 8 imagery(30 m resolution).A spectral index-based classification framework was developed,combining MSAVI with the Normalized Difference Water Index(NDWI)and Salinity Index 1(SI1)to reduce spectral confusion between vegetation,saline soils,and surface water.The MSAVI-based classification achieved an overall accuracy of 77.96%(Kappa coefficient=0.71),supported by 313 field-collected validation points from 2023.While the multi-index approach enabled finer discrimination of ecologically important classes,particularly separating salt pans from solonchak soils,it resulted in a lower overall accuracy(73.80%),highlighting a trade-off between class separability and classification performance.Land cover change analysis revealed a highly dynamic landscape,with 52.96%of the study area transitioning between classes over the decade.Transformed areas(16,893 km2)exceeded stable zones(15,004 km2),driven primarily by rapid desiccation and salinization.Solonchak soils increased at an annual rate of 5.58%,while surface water bodies declined by 4.83%per year.Concurrently,sparse or distressed vegetation increased by 1.43%annually,reflecting ongoing afforestation efforts.This study provides the first MSAVI-based and medium-resolution land cover baseline for the South Aral Seabed and demonstrates that soil-adjusted vegetation indices are essential for reliable dryland classification where conventional indices fail.The proposed spectral index framework offers a replicable methodology applicable to other global drylands facing similar land degradation and restoration challenges.展开更多
The South China Sea suffers strongly from the typhoon storm surge disasters in China,and its northern coastal areas are facing severe risks.Therefore,it is necessary and urgent to establish an assessment system for ra...The South China Sea suffers strongly from the typhoon storm surge disasters in China,and its northern coastal areas are facing severe risks.Therefore,it is necessary and urgent to establish an assessment system for rating typhoon storm surge disaster.We constructed an effective and reliable rating assessment system for typhoon storm surge disaster based on the theories of over-threshold,distribution function family,and composite extreme value.The over-threshold sample was used as the basis of data analysis,the composite extreme value expansion model was used to derive the design water increment,and then the disaster level was delineated based on the return period level.The results of the extreme value model comparison show that the Weibull-Pareto distribution is more suitable than the classical extreme value distribution for fitting the over-threshold samples.The results of the return period projection are relatively stable based on different analysis samples.Taking the 10 typhoon storm surges as examples,they caused landfall in the Guangdong area in the past 10 years.The results of the assessment ranking indicate that the risk levels based on the return period levels obtained from different distributions are generally consistent.When classifying low-risk areas,the classification criteria of the State Oceanic Administration,China(SOA,2012)are more conservative.In the high-risk areas,the results of the assessment ranking based on return period are more consistent with those of the SOA.展开更多
The Third Plenary Session of the 18th CPC Central Committee ushered in a new chapter of China＇s comprehensive deepening of reform. The basic objective of comprehensively deepening reform of the state sector of econom...The Third Plenary Session of the 18th CPC Central Committee ushered in a new chapter of China＇s comprehensive deepening of reform. The basic objective of comprehensively deepening reform of the state sector of economy in the new chapter is to fully integrate this sector with a sophisticated market economic system with the market playing the decisive role in resource allocation. In order to achieve this objective, China is confronted with the four major priorities of adjusting the functions and layout of the state sector of economy according to national mandates, expediting the mixed ownership reform, creating a classified and multi- tiered new system for the administration of the sector, and developing a modern corporate system for SOEs to ensure an efficient micro-level governance mechanism for the sector. （1） The functions of the different types of SOEs should be accurately defined and SOEs should be divided into the three types of public policy SOEs, functional SOEs, and commercial SOEs. This classification forms the premises for reforming the state sector of economy. Based on the functions of the three types of SOEs, the directions and emphases for strategic adjustment should differ as well. （2） The mixed ownership reform should adhere to the methodological principles of combining top-down and bottom-up approaches, implementing pilot programs, and promoting coordinated progress. Practical implementation should ensure fair and standard reform procedures, reform programs consistent with laws and regulations, open and fair equity transfers, as well as fair and transparent internal distributions. The mixed ownership reform of SOEs should introduce the employee stock ownership system and adhere to the principles of compatible incentives, shared growth, and long-term development. Monopolistic sectors should be transformed into competitive market structures to create conditions for the implementation of mixed ownership for SOEs. （3） The new system for the administration of the state sector of economy should comprise three hierarchies： the Commission for the Administration of State Economy at the top level, state capital operation companies or state capital investment companies at the intermediate level and general for-profit enterprises at the bottom level, which administer public policy, functional SOEs, and commercial SOEs respectively. （4） Under the new system for the administration of the state sector of economy characterized by the three hierarchies and categories, the key for perfecting the modern corporate system of SOEs is to establish a differentiated, classified governance mechanism, i.e., different corporate governance mechanisms should be created for SOEs of different functions and roles.展开更多
An analysis with Fourier series on electric signals of meso-spray process of pulse MIG welding of aluminum shows many harmonic waves of different frequency in the signals, including the inherent high, low frequency el...An analysis with Fourier series on electric signals of meso-spray process of pulse MIG welding of aluminum shows many harmonic waves of different frequency in the signals, including the inherent high, low frequency elementary waves of short circuit and the harmonic waves from pulse current besides the noise signals of high frequency. The wavelet filtering with adjustable threshold is applied to study and handle the electric signals from meso-spray process of pulse MIG welding of aluminum, displaying a good solution on suppressing the noise in the signals.展开更多
Fire warning is vital to human life,economy and ecology.However,the development of effective warning systems faces great challenges of fast response,adjustable threshold and remote detecting.Here,we propose an intelli...Fire warning is vital to human life,economy and ecology.However,the development of effective warning systems faces great challenges of fast response,adjustable threshold and remote detecting.Here,we propose an intelligent self-powered remote IoT fire warning system,by employing single-walled carbon nanotube/titanium carbide thermoelectric composite films.The flexible films,prepared by a convenient solution mixing,display p-type characteristic with excellent high-temperature stability,flame retardancy and TE(power factor of 239.7±15.8μW m^(-1) K^(-2))performances.The comprehensive morphology and structural analyses shed light on the underlying mechanisms.And the assembled TE devices(TEDs)exhibit fast fire warning with adjustable warning threshold voltages(1–10 mV).Excitingly,an ultrafast fire warning response time of~0.1 s at 1 mV threshold voltage is achieved,rivaling many state-of-the-art systems.Furthermore,TE fire warning systems reveal outstanding stability after 50 repeated cycles and desired durability even undergoing 180 days of air exposure.Finally,a TED-based wireless intelligent fire warning system has been developed by coupling an amplifier,analogto-digital converter and Bluetooth module.By combining TE characteristics,high-temperature stability and flame retardancy with wireless IoT signal transmission,TE-based hybrid system developed here is promising for next-generation self-powered remote IoT fire warning applications.展开更多
Based on ground observation,lightning locator and atmospheric electric field instrument data,the characteristics of lightning and atmospheric electric field in Nanchang County were analyzed. The warning effect of the ...Based on ground observation,lightning locator and atmospheric electric field instrument data,the characteristics of lightning and atmospheric electric field in Nanchang County were analyzed. The warning effect of the atmospheric electric field instruments on lightning was studied,and the threshold of some atmospheric electric field instruments was adjusted according to the expectation of the warning accuracy rate. In Nanchang County,the annual number of thunderstorm days averaged 48. 6. Lightning mainly occurred from March to August,with a maximum of 8. 8 d in August. The lightning areas were mainly concentrated in the south,followed by the north,and the frequency of lightning in the middle was relatively low. The diurnal variation of lightning was obvious,and lightning happened most frequently from afternoon to evening. Five atmospheric electric field instruments were set up according to the lightning areas of Nanchang County. The average electric field intensity on a sunny day was 0. 06,0. 05,0. 16,0. 07,and 0. 17 kV/m respectively,with certain seasonal variations. The field intensity in June was the lowest in the whole year. The atmospheric electric field on a sunny day also had obvious diurnal variation characteristics,generally presenting the characteristics of double peaks and double valleys. The first peak of atmospheric electric field intensity appeared one hour later than that of relative humidity,and then the change trends were relatively consistent. After the adjustment,the warning accuracy rate of the atmospheric electric field instruments was greatly improved to meet the expectation.展开更多
An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to bal...An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.展开更多
In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold val...In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold value and the classification number is proposed based on the maximum entropy, and the self-adaptive criterion of the classification number is given. The algorithm can obtain thresholds and automatically decide the classification number. Experimental results show that the algorithm is effective.展开更多
针对基于点线特征的实时定位与建图(simultaneous localization and mapping,SLAM)算法在位姿识别过程中对定位精度的要求,提出一种改进单目视觉惯性同步定位与建图(monocular visual-inertial SLAM with efficient point-line flow fea...针对基于点线特征的实时定位与建图(simultaneous localization and mapping,SLAM)算法在位姿识别过程中对定位精度的要求,提出一种改进单目视觉惯性同步定位与建图(monocular visual-inertial SLAM with efficient point-line flow features,EPLF-VINS)算法。首先,分析了梯度阈值参数对line segment detection by edge drawing(EDLines)线段提取算法的影响;其次,在点特征正向光流追踪后采用逆向光流追踪剔除错误追踪点,提高光流追踪正确率;然后,在EPLF-VINS算法的线段提取处融合一种自适应调节算法,通过计算逆向光流追踪后的点特征光流追踪成功率实时地调节梯度阈值参数,从而实现根据环境的变化动态调整线段提取,更好地平衡计算成本与定位精度的效果;最后,基于Robot Operating System(ROS)平台分析了改进EPLF-VINS算法与对比算法在EuRoc和TUM-VI数据集上的轨迹精度与效率。研究结果表明,改进EPLF-VINS算法绘制的轨迹曲线更加贴合真实轨迹,在保证实时性的同时具有更高的定位精度。展开更多
文摘A new classification algorithm for web mining is proposed on the basis of general classification algorithm for data mining in order to implement personalized information services. The building tree method of detecting class threshold is used for construction of decision tree according to the concept of user expectation so as to find classification rules in different layers. Compared with the traditional C4.5 algorithm, the disadvantage of excessive adaptation in C4.5 has been improved so that classification results not only have much higher accuracy but also statistic meaning.
文摘The paper contains a summary of some results of original research total aggregates. The main idea is determining the boundaries of the groups for classification of fuzzy and threshold aggregates using the method of decomposing a mixture of probability distributions. The article presents the experience of partitions of a real aggregate as a finite mixture of probability distributions on private aggregates. Threshold value defined by the boundaries of private aggregates, will match the value of the phenomenon at the intersection of the curves of probability distributions, which extracted from the mixture. The proposed scheme of identification threshold aggregates has found practical application in the research of aggregate of Russian employees by level of payroll and establishing the optimal minimum value monthly wage. The official data of the Federal State Statistics Service were used.
基金Supported by the National Natural Science Foundation of China(No.40675071)~~
文摘In order to assess the climatical and ecological effect which returned the farmland to pasture or forest, the vegetation and crop in Northwest China with suitable threshold value were classified in this experiment by using multi-temporal SPOT/VEGETATION dada and combing supervised classification with unsupervised classification. Compared with the data from Statistical Department and actual investigation, the precision of the classified result was above 85%.
文摘Penile hypersensitivity plays an important role in premature ejaculation （PE）, but differences in penile sensitivity among subtypes of PE are unknown. Therefore, we compared penile sensory thresholds in PE subtypes of lifelong and acquired PE, PE with and without erectile dysfunction （ED）, PE with an intravaginal ejaculation latency time 〈1 min and 〉1 min, and PE with and without orgasmic pleasure perceptual dysfunction. During August 2014 to January 2016, 136 patients with PE were included. Penile warm, cold, and vibratory thresholds were measured. Data of clinical characteristics, sexual life, Premature Ejaculation Diagnostic Tool （PEDT） score, and the 5-item version of the International Index of Erectile Function （IIEF-5） score were collected. Vibratory thresholds of the PE with ED group were higher in the right coronal sulcus （median amplitude： 4.92 vs 3.65 μm, P= 0.02） and the right penile shaft （median amplitude： 3.87 vs 3.30 μm, P = 0.03）, while differences in penile sensory thresholds between other subtypes were not significant. The median PEDT score was lower in the PE without ED group （12 vs 14, P 〈 0.001）. The IIEF-5 and PEDT scores were negatively correlated （r = -0.29, P 〈 0.001）. Patients with orgasmic pleasure perceptual dysfunction had a lower median IIEF-5 score （20 vs 21, P = 0.02）. Patients with PE and ED had lower penile sensitivity, and ED was associated with more severe symptoms and weaker orgasmic pleasure perception. In men with PE, management of comorbid ED is necessary. In case of side effects in erectile function, topical anesthetics should be cautiously used in men with PE and ED.
基金sponsored by National Key R&D Program of China(2018YFC1504504)Youth Foundation of Yunnan Earthquake Agency(2021K01)Project of Yunnan Earthquake Agency“Chuan bang dai”(CQ3-2021001).
文摘In order to improve the accuracy of building structure identification using remote sensing images,a building structure classification method based on multi-feature fusion of UAV remote sensing image is proposed in this paper.Three identification approaches of remote sensing images are integrated in this method:object-oriented,texture feature,and digital elevation based on DSM and DEM.So RGB threshold classification method is used to classify the identification results.The accuracy of building structure classification based on each feature and the multi-feature fusion are compared and analyzed.The results show that the building structure classification method is feasible and can accurately identify the structures in large-area remote sensing images.
文摘In this work, we propose an original approach of semi-vectorial hybrid morphological segmentation for multicomponent images or multidimensional data by analyzing compact multidimensional histograms based on different orders. Its principle consists first of segment marginally each component of the multicomponent image into different numbers of classes fixed at K. The segmentation of each component of the image uses a scalar segmentation strategy by histogram analysis;we mainly count the methods by searching for peaks or modes of the histogram and those based on a multi-thresholding of the histogram. It is the latter that we have used in this paper, it relies particularly on the multi-thresholding method of OTSU. Then, in the case where i) each component of the image admits exactly K classes, K vector thresholds are constructed by an optimal pairing of which each component of the vector thresholds are those resulting from the marginal segmentations. In addition, the multidimensional compact histogram of the multicomponent image is computed and the attribute tuples or ‘colors’ of the histogram are ordered relative to the threshold vectors to produce (K + 1) intervals in the partial order giving rise to a segmentation of the multidimensional histogram into K classes. The remaining colors of the histogram are assigned to the closest class relative to their center of gravity. ii) In the contrary case, a vectorial spatial matching between the classes of the scalar components of the image is produced to obtain an over-segmentation, then an interclass fusion is performed to obtain a maximum of K classes. Indeed, the relevance of our segmentation method has been highlighted in relation to other methods, such as K-means, using unsupervised and supervised quantitative segmentation evaluation criteria. So the robustness of our method relatively to noise has been tested.
基金supported by the United Kingdom(UK)Darwin Initiative(28-003).
文摘The South Aral Seabed is an extreme dryland ecosystem undergoing rapid transformation yet remains misrepresented or absent in global land cover datasets.Conventional vegetation indices,specifically the Normalized Difference Vegetation Index(NDVI),perform poorly in such environments due to their limited ability to distinguish sparse vegetation from highly reflective saline and sandy soils.This study evaluated the effectiveness of the Modified Soil Adjusted Vegetation Index(MSAVI)for improving land cover classification in the South Aral Seabed and conducted a decadal analysis of land cover change between 2013 and 2023 using Landsat 8 imagery(30 m resolution).A spectral index-based classification framework was developed,combining MSAVI with the Normalized Difference Water Index(NDWI)and Salinity Index 1(SI1)to reduce spectral confusion between vegetation,saline soils,and surface water.The MSAVI-based classification achieved an overall accuracy of 77.96%(Kappa coefficient=0.71),supported by 313 field-collected validation points from 2023.While the multi-index approach enabled finer discrimination of ecologically important classes,particularly separating salt pans from solonchak soils,it resulted in a lower overall accuracy(73.80%),highlighting a trade-off between class separability and classification performance.Land cover change analysis revealed a highly dynamic landscape,with 52.96%of the study area transitioning between classes over the decade.Transformed areas(16,893 km2)exceeded stable zones(15,004 km2),driven primarily by rapid desiccation and salinization.Solonchak soils increased at an annual rate of 5.58%,while surface water bodies declined by 4.83%per year.Concurrently,sparse or distressed vegetation increased by 1.43%annually,reflecting ongoing afforestation efforts.This study provides the first MSAVI-based and medium-resolution land cover baseline for the South Aral Seabed and demonstrates that soil-adjusted vegetation indices are essential for reliable dryland classification where conventional indices fail.The proposed spectral index framework offers a replicable methodology applicable to other global drylands facing similar land degradation and restoration challenges.
基金Supported by the National Natural Science Foundation of China(Nos.52071306,52101360)the Natural Science Foundation of Shandong Province(No.ZR2019MEE050)the State Key Laboratory of Coastal and Offshore Engineering(No.LP2104)。
文摘The South China Sea suffers strongly from the typhoon storm surge disasters in China,and its northern coastal areas are facing severe risks.Therefore,it is necessary and urgent to establish an assessment system for rating typhoon storm surge disaster.We constructed an effective and reliable rating assessment system for typhoon storm surge disaster based on the theories of over-threshold,distribution function family,and composite extreme value.The over-threshold sample was used as the basis of data analysis,the composite extreme value expansion model was used to derive the design water increment,and then the disaster level was delineated based on the return period level.The results of the extreme value model comparison show that the Weibull-Pareto distribution is more suitable than the classical extreme value distribution for fitting the over-threshold samples.The results of the return period projection are relatively stable based on different analysis samples.Taking the 10 typhoon storm surges as examples,they caused landfall in the Guangdong area in the past 10 years.The results of the assessment ranking indicate that the risk levels based on the return period levels obtained from different distributions are generally consistent.When classifying low-risk areas,the classification criteria of the State Oceanic Administration,China(SOA,2012)are more conservative.In the high-risk areas,the results of the assessment ranking based on return period are more consistent with those of the SOA.
文摘The Third Plenary Session of the 18th CPC Central Committee ushered in a new chapter of China＇s comprehensive deepening of reform. The basic objective of comprehensively deepening reform of the state sector of economy in the new chapter is to fully integrate this sector with a sophisticated market economic system with the market playing the decisive role in resource allocation. In order to achieve this objective, China is confronted with the four major priorities of adjusting the functions and layout of the state sector of economy according to national mandates, expediting the mixed ownership reform, creating a classified and multi- tiered new system for the administration of the sector, and developing a modern corporate system for SOEs to ensure an efficient micro-level governance mechanism for the sector. （1） The functions of the different types of SOEs should be accurately defined and SOEs should be divided into the three types of public policy SOEs, functional SOEs, and commercial SOEs. This classification forms the premises for reforming the state sector of economy. Based on the functions of the three types of SOEs, the directions and emphases for strategic adjustment should differ as well. （2） The mixed ownership reform should adhere to the methodological principles of combining top-down and bottom-up approaches, implementing pilot programs, and promoting coordinated progress. Practical implementation should ensure fair and standard reform procedures, reform programs consistent with laws and regulations, open and fair equity transfers, as well as fair and transparent internal distributions. The mixed ownership reform of SOEs should introduce the employee stock ownership system and adhere to the principles of compatible incentives, shared growth, and long-term development. Monopolistic sectors should be transformed into competitive market structures to create conditions for the implementation of mixed ownership for SOEs. （3） The new system for the administration of the state sector of economy should comprise three hierarchies： the Commission for the Administration of State Economy at the top level, state capital operation companies or state capital investment companies at the intermediate level and general for-profit enterprises at the bottom level, which administer public policy, functional SOEs, and commercial SOEs respectively. （4） Under the new system for the administration of the state sector of economy characterized by the three hierarchies and categories, the key for perfecting the modern corporate system of SOEs is to establish a differentiated, classified governance mechanism, i.e., different corporate governance mechanisms should be created for SOEs of different functions and roles.
基金This project is supported by National Natural Science Foundation of China（59975068） and Science ＆ Technology Pillar Program of Tianjin（10ZCKFSF00200）.
文摘An analysis with Fourier series on electric signals of meso-spray process of pulse MIG welding of aluminum shows many harmonic waves of different frequency in the signals, including the inherent high, low frequency elementary waves of short circuit and the harmonic waves from pulse current besides the noise signals of high frequency. The wavelet filtering with adjustable threshold is applied to study and handle the electric signals from meso-spray process of pulse MIG welding of aluminum, displaying a good solution on suppressing the noise in the signals.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(2022A1515110296,2022A1515110432)the Shenzhen Science and Technology Program(No.20231120171032001,20231122125728001).
文摘Fire warning is vital to human life,economy and ecology.However,the development of effective warning systems faces great challenges of fast response,adjustable threshold and remote detecting.Here,we propose an intelligent self-powered remote IoT fire warning system,by employing single-walled carbon nanotube/titanium carbide thermoelectric composite films.The flexible films,prepared by a convenient solution mixing,display p-type characteristic with excellent high-temperature stability,flame retardancy and TE(power factor of 239.7±15.8μW m^(-1) K^(-2))performances.The comprehensive morphology and structural analyses shed light on the underlying mechanisms.And the assembled TE devices(TEDs)exhibit fast fire warning with adjustable warning threshold voltages(1–10 mV).Excitingly,an ultrafast fire warning response time of~0.1 s at 1 mV threshold voltage is achieved,rivaling many state-of-the-art systems.Furthermore,TE fire warning systems reveal outstanding stability after 50 repeated cycles and desired durability even undergoing 180 days of air exposure.Finally,a TED-based wireless intelligent fire warning system has been developed by coupling an amplifier,analogto-digital converter and Bluetooth module.By combining TE characteristics,high-temperature stability and flame retardancy with wireless IoT signal transmission,TE-based hybrid system developed here is promising for next-generation self-powered remote IoT fire warning applications.
基金Supported by General Project of Jiangxi Meteorological Bureau in 2018(201818)
文摘Based on ground observation,lightning locator and atmospheric electric field instrument data,the characteristics of lightning and atmospheric electric field in Nanchang County were analyzed. The warning effect of the atmospheric electric field instruments on lightning was studied,and the threshold of some atmospheric electric field instruments was adjusted according to the expectation of the warning accuracy rate. In Nanchang County,the annual number of thunderstorm days averaged 48. 6. Lightning mainly occurred from March to August,with a maximum of 8. 8 d in August. The lightning areas were mainly concentrated in the south,followed by the north,and the frequency of lightning in the middle was relatively low. The diurnal variation of lightning was obvious,and lightning happened most frequently from afternoon to evening. Five atmospheric electric field instruments were set up according to the lightning areas of Nanchang County. The average electric field intensity on a sunny day was 0. 06,0. 05,0. 16,0. 07,and 0. 17 kV/m respectively,with certain seasonal variations. The field intensity in June was the lowest in the whole year. The atmospheric electric field on a sunny day also had obvious diurnal variation characteristics,generally presenting the characteristics of double peaks and double valleys. The first peak of atmospheric electric field intensity appeared one hour later than that of relative humidity,and then the change trends were relatively consistent. After the adjustment,the warning accuracy rate of the atmospheric electric field instruments was greatly improved to meet the expectation.
基金the National Natural Science Foundation of China(No.52175103)。
文摘An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.
文摘In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold value and the classification number is proposed based on the maximum entropy, and the self-adaptive criterion of the classification number is given. The algorithm can obtain thresholds and automatically decide the classification number. Experimental results show that the algorithm is effective.
文摘针对基于点线特征的实时定位与建图(simultaneous localization and mapping,SLAM)算法在位姿识别过程中对定位精度的要求,提出一种改进单目视觉惯性同步定位与建图(monocular visual-inertial SLAM with efficient point-line flow features,EPLF-VINS)算法。首先,分析了梯度阈值参数对line segment detection by edge drawing(EDLines)线段提取算法的影响;其次,在点特征正向光流追踪后采用逆向光流追踪剔除错误追踪点,提高光流追踪正确率;然后,在EPLF-VINS算法的线段提取处融合一种自适应调节算法,通过计算逆向光流追踪后的点特征光流追踪成功率实时地调节梯度阈值参数,从而实现根据环境的变化动态调整线段提取,更好地平衡计算成本与定位精度的效果;最后,基于Robot Operating System(ROS)平台分析了改进EPLF-VINS算法与对比算法在EuRoc和TUM-VI数据集上的轨迹精度与效率。研究结果表明,改进EPLF-VINS算法绘制的轨迹曲线更加贴合真实轨迹,在保证实时性的同时具有更高的定位精度。
