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Search Results: 1 - 10 of 78602 matches for " Xuefeng Chen "
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Chen Xuefeng,

自然资源学报 , 1996,
Abstract: The sustainable development of forest resource is the basis of the coordinative development of forestry and national economy, society and environment. The paper expounds the possibility of forest sustainable development, discusses some problems existing in forest resource development of China and analyses the reasons that cause these problems.
Augmented Lagrangian Methods for Numerical Solutions to Higher Order Differential Equations  [PDF]
Xuefeng Li
Journal of Applied Mathematics and Physics (JAMP) , 2017, DOI: 10.4236/jamp.2017.52021
A large number of problems in engineering can be formulated as the optimization of certain functionals. In this paper, we present an algorithm that uses the augmented Lagrangian methods for finding numerical solutions to engineering problems. These engineering problems are described by differential equations with boundary values and are formulated as optimization of some functionals. The algorithm achieves its simplicity and versatility by choosing linear equality relations recursively for the augmented Lagrangian associated with an optimization problem. We demonstrate the formulation of an optimization functional for a 4th order nonlinear differential equation with boundary values. We also derive the associated augmented Lagrangian for this 4th order differential equation. Numerical test results are included that match up with well-established experimental outcomes. These numerical results indicate that the new algorithm is fully capable of producing accurate and stable solutions to differential equations.
Efficiency Analysis of Electricity, Thermal Power Production and Supply Industries in China  [PDF]
Xuefeng Jiang
American Journal of Industrial and Business Management (AJIBM) , 2019, DOI: 10.4236/ajibm.2019.94065
In this paper, the input-oriented distance function is applied to the efficiency analysis of China’s electricity, thermal power production and supply industries. Due to the obvious gap between China’s east, central and west, we use the metafrontier method to divide the data into three parts according to east, central and west. On the basis of the previous research, this paper makes some innovations in the estimation method, that is, using the two-stage linear programming method to estimate the common boundary input distance function. The results show that the technical efficiency of the eastern, central and western regions is significantly different, which is mainly reflected in that the technical efficiency of the eastern region is higher than that of the central and western regions, and the efficiency gap between the three regions shows no signs of narrowing during the “eleventh five-year plan” and “twelfth five-year plan”. Therefore, the electricity, thermal power production and supply industries in central and western China still need to change the development mode and improve the development quality.
Notes of Numerical Simulation of Summer Rainfall in China with a Regional Climate Model REMO
CUI Xuefeng,HUANG Gang,CHEN Wen,
CUI Xuefeng

大气科学进展 , 2008,
Abstract: Regional climate models are major tools for regional climate simulation and their output are mostly used for climate impact studies. Notes are reported from a series of numerical simulations of summer rainfall in China with a regional climate model. Domain sizes and running modes are major foci. The results reveal that the model in forecast mode driven by "perfect" boundaries could reasonably represent the inter-annual differences: heavy rainfall along the Yangtze River in 1998 and dry conditions in 1997. Model simulation in climate mode differs to a greater extent from observation than that in forecast mode. This may be due to the fact that in climate mode it departs further from the driving fields and relies more on internal model dynamical processes. A smaller domain in climate mode outperforms a larger one. Further development of model parameterizations including dynamic vegetation are encouraged in future studies.
Operation Reliability Assessment for Cutting Tools by Applying a Proportional Covariate Model to Condition Monitoring Information
Gaigai Cai,Xuefeng Chen,Bing Li,Baojia Chen,Zhengjia He
Sensors , 2012, DOI: 10.3390/s121012964
Abstract: The reliability of cutting tools is critical to machining precision and production efficiency. The conventional statistic-based reliability assessment method aims at providing a general and overall estimation of reliability for a large population of identical units under given and fixed conditions. However, it has limited effectiveness in depicting the operational characteristics of a cutting tool. To overcome this limitation, this paper proposes an approach to assess the operation reliability of cutting tools. A proportional covariate model is introduced to construct the relationship between operation reliability and condition monitoring information. The wavelet packet transform and an improved distance evaluation technique are used to extract sensitive features from vibration signals, and a covariate function is constructed based on the proportional covariate model. Ultimately, the failure rate function of the cutting tool being assessed is calculated using the baseline covariate function obtained from a small sample of historical data. Experimental results and a comparative study show that the proposed method is effective for assessing the operation reliability of cutting tools.
GO-Diff: Mining functional differentiation between EST-based transcriptomes
Zuozhou Chen, Weilin Wang, Xuefeng Ling, Jane Liu, Liangbiao Chen
BMC Bioinformatics , 2006, DOI: 10.1186/1471-2105-7-72
Abstract: Here we present GO-Diff, a GO-based functional profiling approach towards high throughput EST-based gene expression analysis and comparative transcriptomics. Utilizing holistic gene expression information, the software converts EST frequencies into EST Coverage Ratios of GO Terms. The ratios are then tested for statistical significances to uncover differentially represented GO terms between the compared transcriptomes, and functional differences are thus inferred. We demonstrated the validity and the utility of this software by identifying differentially represented GO terms in three application cases: intra-species comparison; meta-analysis to test a specific hypothesis; inter-species comparison. GO-Diff findings were consistent with previous knowledge and provided new clues for further discoveries. A comprehensive test on the GO-Diff results using series of comparisons between EST libraries of human and mouse tissues showed acceptable levels of consistency: 61% for human-human; 69% for mouse-mouse; 47% for human-mouse.GO-Diff is the first software integrating EST profiles with GO knowledge databases to mine functional differentiation between biological systems, e.g. tissues of the same species or the same tissue cross species. With rapid accumulation of EST resources in the public domain and expanding sequencing effort in individual laboratories, GO-Diff is useful as a screening tool before undertaking serious expression studies.Cellular development and its associated biochemical processes within and between various cell types are determined by the relevant cellular proteomes, which are tightly regulated by biochemical synthesis, different stage genetic interactions and various metabolic pathways. The proteome of a cell is largely (but not exclusively) regulated by gene expression [1], and the transcriptome can be regarded as a sensitive read-out of the proteome revealing the biochemical state of the cell. Currently the most popular gene expression analysis platfo
Rpb1 Sumoylation in Response to UV Radiation or Transcriptional Impairment in Yeast
Xuefeng Chen, Baojin Ding, Danielle LeJeune, Christine Ruggiero, Shisheng Li
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005267
Abstract: Covalent modifications of proteins by ubiquitin and the Small Ubiquitin-like MOdifier (SUMO) have been revealed to be involved in a plethora of cellular processes, including transcription, DNA repair and DNA damage responses. It has been well known that in response to DNA damage that blocks transcription elongation, Rpb1, the largest subunit of RNA polymerase II (Pol II), is ubiquitylated and subsequently degraded in mammalian and yeast cells. However, it is still an enigma regarding how Pol II responds to damaged DNA and conveys signal(s) for DNA damage-related cellular processes. We found that Rpb1 is also sumoylated in yeast cells upon UV radiation or impairment of transcription elongation, and this modification is independent of DNA damage checkpoint activation. Ubc9, an E2 SUMO conjugase, and Siz1, an E3 SUMO ligase, play important roles in Rpb1 sumoylation. K1487, which is located in the acidic linker region between the C-terminal domain and the globular domain of Rpb1, is the major sumoylation site. Rpb1 sumoylation is not affected by its ubiquitylation, and vice versa, indicating that the two processes do not crosstalk. Abolishment of Rpb1 sumoylation at K1487 does not affect transcription elongation or transcription coupled repair (TCR) of UV-induced DNA damage. However, deficiency in TCR enhances UV-induced Rpb1 sumoylation, presumably due to the persistence of transcription-blocking DNA lesions in the transcribed strand of a gene. Remarkably, abolishment of Rpb1 sumoylation at K1487 causes enhanced and prolonged UV-induced phosphorylation of Rad53, especially in TCR-deficient cells, suggesting that the sumoylation plays a role in restraining the DNA damage checkpoint response caused by transcription-blocking lesions. Our results demonstrate a novel covalent modification of Rpb1 in response to UV induced DNA damage or transcriptional impairment, and unravel an important link between the modification and the DNA damage checkpoint response.
A Monotonic Degradation Assessment Index of Rolling Bearings Using Fuzzy Support Vector Data Description and Running Time
Zhongjie Shen,Zhengjia He,Xuefeng Chen,Chuang Sun,Zhiwen Liu
Sensors , 2012, DOI: 10.3390/s120810109
Abstract: Performance degradation assessment based on condition monitoring plays an important role in ensuring reliable operation of equipment, reducing production downtime and saving maintenance costs, yet performance degradation has strong fuzziness, and the dynamic information is random and fuzzy, making it a challenge how to assess the fuzzy bearing performance degradation. This study proposes a monotonic degradation assessment index of rolling bearings using fuzzy support vector data description (FSVDD) and running time. FSVDD constructs the fuzzy-monitoring coefficient?which is sensitive to the initial defect and stably increases as faults develop. Moreover, the parameter describes the accelerating relationships between the damage development and running time. However, the index?with an oscillating trend disagrees with the irreversible damage development. The running time is introduced to form a monotonic index, namely damage severity index (DSI). DSI inherits all advantages of and overcomes its disadvantage. A run-to-failure test is carried out to validate the performance of the proposed method. The results show that DSI reflects the growth of the damages with running time perfectly.
Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control
Xingwu Zhang,Xuefeng Chen,Shangqin You,Zhengjia He,Bing Li
Sensors , 2012, DOI: 10.3390/s120404986
Abstract: In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC) is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results.
Molecular characterization of a mosaic locus in the genome of 'Candidatus Liberibacter asiaticus'
Xuefeng Wang, Changyong Zhou, Xiaoling Deng, Huanan Su, Jianchi Chen
BMC Microbiology , 2012, DOI: 10.1186/1471-2180-12-18
Abstract: A genomic region (CLIBASIA_05640 to CLIBASIA_05650) of 'Ca. L. asiaticus' showing hyper-sequence variation or locus mosaicism was identified and investigated using 262 bacterial strains (188 from China and 74 from Florida). Based on the characteristic electrophoretic profiles of PCR amplicons generated by a specific primer set, eight electrophoretic types (E-types) were identified, six E-types (A, B, C, D, E, and F) in China and four E-types (A, C, G, and H) in Florida. The 'Ca. L. asiaticus' strains from China consisted predominately of E-type A (71.3%) and E-type B (19.7%). In contrast, the 'Ca. L. asiaticus' strains from Florida was predominated by E-type G (82.4%). Diversity of 'Ca. L. asiaticus' in China was also evidenced. Strains from the high altitude Yunnan Province consisted of five E-types with E-type B being the majority (62.8%), whereas strains from the low altitude coastal Guangdong Province consisted of only two E-types with E-type A as the majority (97.0%). Sequence analyses revealed that variation of DNA amplicons was due to insertion/deletion events at CLIBASIA_05650 and the downstream intergenic region.This study demonstrated the genomic mosaicism of 'Ca. L. asiaticus' resulted from active DNA insertion/deletion activities. Analyses of strain variation depicted the significant inter- and intra-continent diversity of 'Ca. L. asiaticus'.Huanglongbing (HLB) is a destructive disease of citrus production worldwide. All known commercial citrus cultivars are susceptible to HLB. The disease was first noted in Chaoshan area in Guangdong Province of the People's Republic of China in the late of 1800s [1] and is currently distributed in 10 citrus producing provinces in South China. HLB is now established in Sao Paulo of Brazil [2] and Florida of the United States [3] where it poses a great threat to the citrus industry. The disease is associated with three species of non-culturable, phloem-limited, α-Proteobacteria: 'Candidatus Liberibacter asiaticus', 'Ca.
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