Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient metho...Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient method is proposed which is featured by extracting only a few necessary curves from the check surface instead of sampling the entire surface. By rotating and compressing the 3 D check surface relative to all tool postures, the boundaries of the area occupied by the 2 D compressed surfaces are the essential elements for determining the shortest tool length. A tracking-based numerical algorithm is introduced to efficiently solve the silhouette curves which are formed in compressing. To define the multi-taper shaped tool holding system(THS) which is commonly used in production, a characterization model for THS profile is established. A model for solving the shortest tool length is finally constructed based on the critical interference relationship between the THS profile and all compressed boundary curves. For acceleration, the boundary splines are segmented according to their knot vectors. Then a new concept called the axis-aligned tool length box(AATB) is introduced,which can provide a conservative range of tool length for a spline segment. By scanning the AATBs of all spline segments, the very few effective spline segments that may ultimately determine the shortest tool length are filtered out. This acceleration method makes the solution for the shortest tool length more focused and efficient. The results of experimental examples are also reported to validate the efficiency and accuracy of the proposed algorithm.展开更多
In several stress responsive gene loci of monocot cereal crops,we have previously identified an unusual posttranscriptional processing mediated by paired presence of short direct repeated （SDR） sequences at 5＇ and ...In several stress responsive gene loci of monocot cereal crops,we have previously identified an unusual posttranscriptional processing mediated by paired presence of short direct repeated （SDR） sequences at 5＇ and 3＇ splicing junctions that are distinct from conventional （U2/U12-type） splicing boundaries.By using the known SDR-containing sequences as probes,24 plant candidate genes involved in diverse functional pathways from both monocots and dicots that potentially possess SDR-mediated posttranscriptional processing were predicted in the GenBank database.The SDRs-mediated posttranscriptional processing events including cis-and trans-actions were experimentally detected in majority of the predicted candidates.Extensive sequence analysis demonstrates several types of SDR-associated splicing peculiarities including partial exon deletion,exon fragment repetition,exon fragment scrambling and trans-splicing that result in either loss of partial exon or unusual exonic sequence rearrangements within or between RNA molecules.In addition,we show that the paired presence of SDR is necessary but not sufficient in SDR-mediated splicing in transient expression and stable transformation systems.We also show prokaryote is incapable of SDR-mediated premRNA splicing.展开更多
Smart, real-time, low-cost, and distributed ecosystem monitoring is essential for understanding and managing rapidly changing ecosystems. However, new techniques in the big data era have rarely been introduced into op...Smart, real-time, low-cost, and distributed ecosystem monitoring is essential for understanding and managing rapidly changing ecosystems. However, new techniques in the big data era have rarely been introduced into operational ecosystem monitoring, particularly for fragile ecosystems in remote areas.We introduce the Internet of Things(IoT) techniques to establish a prototype ecosystem monitoring system by developing innovative smart devices and using IoT technologies for ecosystem monitoring in isolated environments. The developed smart devices include four categories: large-scale and nonintrusive instruments to measure evapotranspiration and soil moisture, in situ observing systems for CO2 and d13 C associated with soil respiration, portable and distributed devices for monitoring vegetation variables, and Bi-CMOS cameras and pressure trigger sensors for terrestrial vertebrate monitoring. These new devices outperform conventional devices and are connected to each other via wireless communication networks. The breakthroughs in the ecosystem monitoring IoT include new data loggers and longdistance wireless sensor network technology that supports the rapid transmission of data from devices to wireless networks. The applicability of this ecosystem monitoring IoT is verified in three fragile ecosystems, including a karst rocky desertification area, the National Park for Amur Tigers, and the oasis-desert ecotone in China. By integrating these devices and technologies with an ecosystem monitoring information system, a seamless data acquisition, transmission, processing, and application IoT is created. The establishment of this ecosystem monitoring IoT will serve as a new paradigm for ecosystem monitoring and therefore provide a platform for ecosystem management and decision making in the era of big data.展开更多
Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the ...Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the analytic hierarchy process(AHP)method is used to calculate the weight of the factors in evaluations of freeze-thaw erosion,but this method cannot accurately depict the fuzziness and randomness of the problem.To overcome this disadvantage,this study proposed an improved AHP method based on the cloud model for the evaluation of the factors impacting freeze-thaw erosion.To establish an improved evaluation method for freeze-thaw erosion in Tibet,the following six factors were selected:mean annual air temperature,mean annual ground surface temperature,average annual precipitation,aspect,vegetation coverage,and topographic relief.The traditional AHP and the cloud model were combined to assign the weights of the impacting factors,and a consistency check was performed.The comprehensive evaluation index model was used to evaluate the intensity of freeze-thaw erosion in Tibet.The results show that freeze-thaw erosion is extensive,stretching over approximately 66.1%of Tibet.Moreover,mild erosion and moderate erosion are the most widely distributed erosion intensity levels,accounting for 36.4%and 34.4%of the total freeze-thaw erosion,respectively.The intensity of freeze-thaw erosion gradually increased from slight erosion in the northwest to severe erosion in the southeast of the study region.The evaluation results for the intensity and distribution of freeze-thaw erosion in Tibet were confirmed to be consistent with the actual situation.In brief,this study supplies a new approach for quantitatively evaluating the intensity of freeze-thaw erosion in Tibet.展开更多
基金support of National Science and Technology Major Project of China (No. JPPTKF2016)。
文摘Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient method is proposed which is featured by extracting only a few necessary curves from the check surface instead of sampling the entire surface. By rotating and compressing the 3 D check surface relative to all tool postures, the boundaries of the area occupied by the 2 D compressed surfaces are the essential elements for determining the shortest tool length. A tracking-based numerical algorithm is introduced to efficiently solve the silhouette curves which are formed in compressing. To define the multi-taper shaped tool holding system(THS) which is commonly used in production, a characterization model for THS profile is established. A model for solving the shortest tool length is finally constructed based on the critical interference relationship between the THS profile and all compressed boundary curves. For acceleration, the boundary splines are segmented according to their knot vectors. Then a new concept called the axis-aligned tool length box(AATB) is introduced,which can provide a conservative range of tool length for a spline segment. By scanning the AATBs of all spline segments, the very few effective spline segments that may ultimately determine the shortest tool length are filtered out. This acceleration method makes the solution for the shortest tool length more focused and efficient. The results of experimental examples are also reported to validate the efficiency and accuracy of the proposed algorithm.
基金supported by the National Key Basic Research Program (973 program) (No. 2006CB100205)the National Science Fund for Distinguished Young Scholars (No. 30825030)+2 种基金the National Natural Science Foundation of China (No. 30770466, 90717110, 30970260 and 30971752)the Earmarked Fund for Modern Agro-industry Technology Research System (No. nycytx-01)the National High Technology Research and Development Program of China (863 Program) (No. 2007AA10Z100)
文摘In several stress responsive gene loci of monocot cereal crops,we have previously identified an unusual posttranscriptional processing mediated by paired presence of short direct repeated （SDR） sequences at 5＇ and 3＇ splicing junctions that are distinct from conventional （U2/U12-type） splicing boundaries.By using the known SDR-containing sequences as probes,24 plant candidate genes involved in diverse functional pathways from both monocots and dicots that potentially possess SDR-mediated posttranscriptional processing were predicted in the GenBank database.The SDRs-mediated posttranscriptional processing events including cis-and trans-actions were experimentally detected in majority of the predicted candidates.Extensive sequence analysis demonstrates several types of SDR-associated splicing peculiarities including partial exon deletion,exon fragment repetition,exon fragment scrambling and trans-splicing that result in either loss of partial exon or unusual exonic sequence rearrangements within or between RNA molecules.In addition,we show that the paired presence of SDR is necessary but not sufficient in SDR-mediated splicing in transient expression and stable transformation systems.We also show prokaryote is incapable of SDR-mediated premRNA splicing.
基金supported by the National Key Research & Development Program of China (2016YFC0500106)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA20100104)the 13th Five-year Informatization Plan of the Chinese Academy of Sciences (XXH13505-06)
文摘Smart, real-time, low-cost, and distributed ecosystem monitoring is essential for understanding and managing rapidly changing ecosystems. However, new techniques in the big data era have rarely been introduced into operational ecosystem monitoring, particularly for fragile ecosystems in remote areas.We introduce the Internet of Things(IoT) techniques to establish a prototype ecosystem monitoring system by developing innovative smart devices and using IoT technologies for ecosystem monitoring in isolated environments. The developed smart devices include four categories: large-scale and nonintrusive instruments to measure evapotranspiration and soil moisture, in situ observing systems for CO2 and d13 C associated with soil respiration, portable and distributed devices for monitoring vegetation variables, and Bi-CMOS cameras and pressure trigger sensors for terrestrial vertebrate monitoring. These new devices outperform conventional devices and are connected to each other via wireless communication networks. The breakthroughs in the ecosystem monitoring IoT include new data loggers and longdistance wireless sensor network technology that supports the rapid transmission of data from devices to wireless networks. The applicability of this ecosystem monitoring IoT is verified in three fragile ecosystems, including a karst rocky desertification area, the National Park for Amur Tigers, and the oasis-desert ecotone in China. By integrating these devices and technologies with an ecosystem monitoring information system, a seamless data acquisition, transmission, processing, and application IoT is created. The establishment of this ecosystem monitoring IoT will serve as a new paradigm for ecosystem monitoring and therefore provide a platform for ecosystem management and decision making in the era of big data.
基金funded by the National Key Research and Development Program of China(No.2017YFB0503500)the Shandong Provincial Natural Science Foundation(Nos.ZR2020MD015 and ZR2020MD018)+1 种基金the Guangdong Academy of Sciences to build First-rate Research Institution Special Fund for Action Project(No.2019GDASYL-0103003)the Young Teacher Development Support Program of Shandong University of Technology(No.4072-115016).
文摘Freeze-thaw erosion can lead to accelerated soil loss,which is an important factor related to soil erosion in cold regions.Tibet is a typical region that is seriously affected by freeze-thaw erosion.Traditionally,the analytic hierarchy process(AHP)method is used to calculate the weight of the factors in evaluations of freeze-thaw erosion,but this method cannot accurately depict the fuzziness and randomness of the problem.To overcome this disadvantage,this study proposed an improved AHP method based on the cloud model for the evaluation of the factors impacting freeze-thaw erosion.To establish an improved evaluation method for freeze-thaw erosion in Tibet,the following six factors were selected:mean annual air temperature,mean annual ground surface temperature,average annual precipitation,aspect,vegetation coverage,and topographic relief.The traditional AHP and the cloud model were combined to assign the weights of the impacting factors,and a consistency check was performed.The comprehensive evaluation index model was used to evaluate the intensity of freeze-thaw erosion in Tibet.The results show that freeze-thaw erosion is extensive,stretching over approximately 66.1%of Tibet.Moreover,mild erosion and moderate erosion are the most widely distributed erosion intensity levels,accounting for 36.4%and 34.4%of the total freeze-thaw erosion,respectively.The intensity of freeze-thaw erosion gradually increased from slight erosion in the northwest to severe erosion in the southeast of the study region.The evaluation results for the intensity and distribution of freeze-thaw erosion in Tibet were confirmed to be consistent with the actual situation.In brief,this study supplies a new approach for quantitatively evaluating the intensity of freeze-thaw erosion in Tibet.
