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An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction

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Journal of Mountain Science 2017年第6期14卷 1161-1173页

作者： HOU Tian-xing xu Qiang XIE Hong-qiang xu Nu-wen ZHOU Jia-wen State Key Laboratory of Hydraulics and Mountain River Engineering Siehuan University Chengdu 610065 China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology Chengdu 610059 China College of Water Resource and Hydropower Sichuan University Chengdu 610065 China

Mountain hazards with large masses of rock blocks in motion – such as rock falls, avalanches and landslides – threaten human lives and structures. Dynamic fragmentation is a common phenomenon during the movement process of rock blocks in rock avalanche, due to the high velocity and impacts against obstructions. In view of the energy consumption theory for brittle rock fragmentation proposed by Bond, which relates energy to size reduction, a theoretical model is proposed to estimate the average fragment size for a moving rock block when it impacts against an obstruction. Then, different forms of motion are studied, with various drop heights and slope angles for the moving rock block. The calculated results reveal that the average fragment size decreases as the drop height increases, whether for free-fall or for a sliding or rolling rock block, and the decline in size is rapid for low heights and slow for increasing heights in the corresponding curves. Moreover, the average fragment size also decreases as the slope angle increases for a slidingrock block. In addition, a rolling rock block has a higher degree of fragmentation than a sliding rock block, even for the same slope angle and block volume. Finally, to compare with others' results, the approximate number of fragments is estimated for each calculated example, and the results show that the proposed model is applicable to a relatively isotropic moving rock block.

关键词： Rock block Rock fragmentation Rock movement process Crushing work ratio Average fragment size

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Tetraalkyl-substituted zinc phthalocyanines used as anode buffer layers for organic light-emitting diodes

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Chinese Physics B 2020年第1期29卷 417-423页

作者： Qian Chen Songhe Yang Lei Dong Siyuan Cai Jiaju xu Zongxiang xu Department of Chemistry Southern University of Science and TechnologyShenzhen 518055China

Two soluble tetraalkyl-substituted zinc phthalocyanines(ZnPcs)for use as anode buffer layer materials in tris(8-hydroxyquinoline)aluminum(Alq3)-based organic light-emitting diodes(OLEDs)are presented in this *** holeblocking properties of these Zn Pc layers slowed the hole injection process into the Alq3 emissive layer greatly and thus reduced the production of unstable cationic Alq3(Alq3^+)*** led to the enhanced brightness and efficiency when compared with the corresponding properties of OLEDs based on the popular poly-(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)buffer ***,because of the high thermal and chemical stabilities of these Zn Pcs,a nonaqueous film fabrication process was realized together with improved charge balance in the OLEDs and enhanced OLED lifetimes.

关键词： organic light-emitting diode anode buffer layer metal phthalocyanine solution process

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Novel detection method for DC series arc faults by using morphological filtering

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The Journal of China Universities of Posts and Telecommunications 2015年第5期22卷 84-91页

作者： Chen Luping Wang Peng xu Liangjun School of Automation Beijing University of Posts and Telecommunications

It has been known that DC arc faults pose a hazard in power electronics systems. Due to the fault current is lower than normal current load, series arc is more difficult to be discovered than parallel arc. The traditional methods of DC series arc faults detection have some disadvantages, such as large computation, long delay and easier influence by interferences. In this paper, a novel method with multi-scale morphological filtering was utilized for the fault detection of DC series arc. Compared to the tradition method, the proposed method is more simple and efficient. It was verified that it was convenient for field application of on-line monitoring and diagnosis with a good ability to prevent misjudgments from the environment interference.

关键词： arc fault DC series arc mathematical morphology st

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Submillimeter/millimeter observations of the high-mass star forming region IRAS 22506+5944

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Research in Astronomy and Astrophysics 2010年第2期10卷 151-158页

作者： Jin-Long xu Jun-Jie Wang National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China NAOC-TU Joint Center for Astrophysics Lhasa 850000 China

The mapping observations of CO J -- 2-1, CO J = 3- 2, 13CO J = 2-1 and 13CO J -- 3 - 2 lines in the direction of IRAS 22506＋5944 have been made. The results show that the cores in the J = 2 - i transition lines have a similar morphology to those in the J -- 3 - 2 transition lines. Bipolar molecular outflows are verified. The prior IRAS 22506＋5944 observations indicated that two IRAS sources and three H20 masers were located close to the peak position of the core. One of the IRAS sources may be the driving source of the outflows. In addition, the H20 masers may occur in relatively warm environments. The parameters of the dense core and outflow, obtained by the LTE method, indicate that IRAS 22506＋5944 is a high-mass star formation region.

关键词： ISM: jets and outflows -- ISM: kinematics and dynamics -- ISM molecules -- stars: formation

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Emergy footprint evaluation of hydropower projects

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Science China(Technological Sciences) 2013年第9期56卷 2336-2342页

作者： WU JianHua HE ChengLong xu WeiLin College of Water Conservancy and Hydropower Engineering Hohai University State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University

In the past thirty years, various hydropower projects, some with a dam height of over 300 m, have been planned and constructed within China. It is inevitable that these will have sizable effects on the environment, and it is crucial therefore to reasonably evaluate and control adverse effects. In this paper, the transformities of various items for hydropower projects were systematically analyzed, and an emergy footprint model for the projects was developed based on ecological footprint analyses and emergy theory, so that it can quantitatively evaluate the effects on the environment, both positive and negative, resulting from the whole process of planning, constructing and operating the projects. As an example, the effects of a large-scale hydropower project, the 'LP project', were investigated. The results showed that the hydropower projects have strong positive effects on the environment and can even in the short term balance the emergy footprint appropriation resulting from the construction and operation of the hydropower projects. Finally, suggestions were presented for the design of hydropower projects.

关键词： ecological footprint emergy emergy footprint model environment hydropower project transformity

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Energy-Efficient Mobile Data Collection Adopting Node Cooperation in an Underwater Acoustic Sensor Network

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China Communications 2017年第6期14卷 32-42页

作者： Yougan Chen Xiaoting Jin Xiaomei xu Key Laboratory of Underwater Acoustic Communication and Marine Information Technology (Xiamen University) Ministry of Education Xiamen 361005 China Department of Applied Ocean Physics and Engineering Xiamen University Xiamen 361102 China

This paper considers an underwater acoustic sensor network with one mobile surface node to collect data from multiple underwater nodes,where the mobile destination requests retransmission from each underwater node individually employing traditional automatic-repeat-request(ARQ) *** propose a practical node cooperation(NC) protocol to enhance the collection efficiency,utilizing the fact that underwater nodes can overhear the transmission of *** reduce the source level of underwater nodes,the underwater data collection area is divided into several sub-zones,and in each sub-zone,the mobile surface node adopting the NC protocol could switch adaptively between selective relay cooperation(SRC) and dynamic network coded cooperation(DNC) .The difference of SRC and DNC lies in whether or not the selected relay node combines the local data and the data overheard from undecoded node(s) to form network coded packets in the retransmission *** NC protocol could also be applied across the sub-zones due to the wiretap *** addition,we investigate the effects of different mobile collection paths,collection area division and cooperative zone design for energy *** numerical results showthat the proposed NC protocol can effectively save energy compared with the traditional ARQ scheme.

关键词： underwater acoustic sensor networks mobile data collection node cooperation cooperative communications energy efficiency

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High-dimensional *** Problem over Short Intervals

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Acta Mathematica Sinica,English Series 2014年第2期30卷 213-228页

作者： Zhe Feng xu Tian Ping ZHANG Department of Mathematics Northwest University College of Mathematics and Information Science Shaanxi Normal University

Letk be a positive integer and n a nonnegative integer,0 〈 λ1,...,λk＋1 ≤ 1 be real numbers and w =（λ1,λ2,...,λk＋1）.Let q ≥ max{[1/λi ]：1 ≤ i ≤ k ＋ 1} be a positive integer,and a an integer coprime to *** by N（a,k,w,q,n） the 2n-th moment of（b1··· bk c） with b1··· bk c ≡ a（mod q）,1 ≤ bi≤λiq（i = 1,...,k）,1 ≤ c ≤λk＋1 q and 2（b1＋ ··· ＋ bk ＋ c）.We first use the properties of trigonometric sum and the estimates of n-dimensional Kloosterman sum to give an interesting asymptotic formula for N（a,k,w,q,n）,which generalized the result of *** we use the properties of character sum and the estimates of Dirichlet L-function to sharpen the result of N（a,k,w,q,n） in the case ofw =（1/2,1/2,...,1/2） and n = *** order to show our result is close to the best possible,the mean-square value of N（a,k,q） φk（q）/2k＋2and the mean value weighted by the high-dimensional Cochrane sum are studied too.

关键词： D. H. Lehmer problem short intervals trigonometric sum character sum Cochrane sum

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Lifted System Framework for Learning Control with Different Trial Lengths

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International Journal of Automation and computing 2015年第3期12卷 273-280页

作者： xue-Fang Li Jian-Xin xu Department of Electrical and Computer Engineering National University of Singapore

This paper addresses an iterative learning control(ILC) design problem for discrete-time linear systems with randomly varying trial lengths. Due to the variation of the trial lengths, a stochastic matrix and an iteration-average operator are introduced to present a unified expression of ILC scheme. By using the framework of lifted system, the learning convergence condition of ILC in mathematical expectation is derived without using λ-norm. It is shown that the requirement on classic ILC that all trial lengths must be identical is mitigated and the identical initialization condition can be also removed. In the end, two illustrative examples are presented to demonstrate the performance and the effectiveness of the proposed ILC scheme for both time-invariant and time-varying linear systems.

关键词： Iterative learning control average operator randomly varying trial lengths identical initialization condition lifted sys-tem.

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Cushioning Performance of Hilbert Fractal Sandwich Packaging Structures under Quasi-Static Compressions

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Computer Modeling in Engineering & Sciences 2023年第4期135卷 275-292页

作者： Xingye xu Haiyan Song Lijun Wang College of Light Industry Science and Engineering Tianjin University of Science&TechnologyTianjin300457China Key Laboratory of Food Packaging Materials and Technology of China Light Industry Tianjin300457China

The sandwich structure of cushioning packaging has an important influence on the cushioning *** fractal theory is an important graphic *** on Hilbert fractal theory,a new sandwich structure was *** generation mechanism and recurrence formula of theHilbert fractal were expressed by Lin’s language,and the second-orderHilbert sandwich structure was constructed fromthermoplastic *** constitutive model of the hyperelastic body was established by using the finite element *** the unit mass energy absorption as the optimization goal,the fractal sandwich structure was optimized,and the best result was obtained when the order was 2.5 and the unit layer thickness was 0.75 *** sandwich structure was compared with the rice-shaped sandwich structure commonly used in industry,and the Hilbert fractal structure had better energy *** has practical significance for the development and application of newcushioning packaging structures.

关键词： Hilbert fractal sandwich structure static compression buffer packaging

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Suppression of super-knock in TC-GDI engine using two-stage injection in intake stroke(TSII)

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Science China(Technological Sciences) 2014年第1期57卷 80-85页

作者： WANG Zhi xu YaQi WANG JianXin State Key Laboratory of Automotive Safety and Energy Tsinghua University

Turbocharging and direct injection are main technologies used for energy-saving gasoline engines. But the biggest challenge is super-knock, whose mechanism is unclear and has no effective strategy to suppress this super-knock until now. The effects of injection strategies on super-knock were experimentally investigated in a turbocharged GDI engine. It was found that two-stage injections during intake stroke （TSII） can eliminate super-knock. Meanwhile, the fuel consumption, emissions and exhaust tem- perature can keep optimized level. By sweeping the start of the 1st injection （SOIl）, end of the 2nd injection （EOI2） and the split injection ratios （ROI2） using 5000 cycles evaluation test at low-speed high load operating point, the optimized injection strategy for the typical TC-GDI engine is TSII with SOIl at middle of intake stroke, EOI2 at end of intake stroke, and ROI2 of 0.3.

关键词： turbocharged GDI engine super-knock injection strategies two-stage injections in intake stroke (TSII)

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