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AN OSCILLATION CRITERIA FOR SECOND ORDERFUNCTIONAL EQUATIONS

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Acta Mathematica Scientia 2002年第1期22卷 56-62页

作者：申建华 ip. Stavroulakis Department of Mathematics Hunan Normal University Changsha 410081 China Department of Mathematics University of Ioannina 451 10 Ioannina Greece

This paper is concerned with the oscillation of second order linear functional equations of the form x(g(t)) = p(t)x(t) + Q(t)X(g(2)(t)), Where p, Q, g : [t(0), infinity) --> R+ = [0, infinity) are given real valued functions such that g(t) not equivalent to t, lim(t-->infinity) g(t) = infinity. It is proved here that when 0 less than or equal to m := lim inf(t-->infinity) Q(t)P(g(t)) less than or equal to 1/4 all solutions of this equation oscillate if the condition lim(t-->infinity) sup Q(t)P(g(t)) > (1 + root1 -4m/2)(2) (*) is satisfied. It should be emphasized that the condition (*) can not be improved in some sense.

关键词： oscillation nonoscillation functional equations

Review of Alloy Membranes/Films for Hydrogen Separation or Purification

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Journal of Rare Earths 2005年第S1期23卷 611-616页

作者：王仲民 Li Vanessa Sammy Lap-ip Chan Department of Information Science and Engineering Guilin University of Electronic Technology Guilin 541004 China School of Material Science and Engineering University of New South Wales Sydney NSW 2052 Australia

Hydrogen separation and purification are two important chemical processes in the extensive application of hydrogen energy. Membrane technology has opened up a potential solution to the problems of separation and purification in an energy effective way. Membranes of adequate hydrogen permeability, good thermal and mechanical stability are the key to successful application of membrane technology in hydrogen separation and purification. In this paper, the relative parameters concerning hydrogen permeability, the development of different types of membranes namely: palladium composite membranes; V-based alloy membranes, specific functionality embraced alloy membranes, metal hydride (MH) thin films and fabrications, were reviewed and discussed. Pd-free membranes are found to be the ideal alternatives. Suitable MH thin films with mono- or multi-layer microstructures produced by novel fabrication techniques, is likely to be the promising candidates due to possessing properties distinct from those of bulk materials in membrane form.

关键词： hydrogen separation and purification membrane thin film hydrogen permeability

Field test of multi-hop image sensing network prototype on a city-wide scale

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Digital Communications and Networks 2019年第2期5卷 131-137页

作者： Xianhui Che Barry ip Zhuge Yan School of Computer Science University of HertfordshireALIO 9GHUK Robert Kennedy College Technoparkstrasse 18005 ZurichSwitzerland Department of Electrical and Electronic Engineering University of Nottingham Ningbo Campus315100NingboChina

Wireless multimedia sensor networks drastically stretch the horizon of traditional monitoring and surveillance systems. Most existing research has utilized Zigbee or WiFi as the communication technology. Both technologies use ultra-high frequencies (primarily 2.4 GHz) and suffer from a relatively short transmission range (i.e., 100 m line-of-sight). The objective of this study is to assess the feasibility and potential of transmitting image information using RF modules with lower frequencies (e.g., 433 MHz) to achieve a larger-scale deployment as in a city scenario. The Arduino platform is used because of its low cost and simplicity. Details of hardware properties are provided in this article, and we investigate optimum configurations for the system. After achieving an initial range test transmission distance of more than 2000 m line-of-sight, the prototype network is installed in a real life city plot for further examination of performance. A range of suitable applications is proposed and suggestions for future research are provided.

关键词： Image sensing Prototype Field test

Model Checking for a General Linear Model with Nonignorable Missing Covariates

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Acta Mathematicae Applicatae Sinica 2012年第1期28卷 99-110页

作者： Zhi-hua SUN Wai-Cheung ip Heung WONG School of Mathematical sciences Graduate University of Chinese Academy of SciencesBeijing 100049China Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China Department of Applied Mathematics Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina

In this paper, we investigate the model checking problem for a general linear model with nonignorable missing covariates. We show that, without any parametric model assumption for the response probability, the least squares method yields consistent estimators for the linear model even if only the complete data are applied. This makes it feasible to propose two testing procedures for the corresponding model checking problem： a score type lack-of-fit test and a test based on the empirical process. The asymptotic properties of the test statistics are investigated. Both tests are shown to have asymptotic power 1 for local alternatives converging to the null at the rate n-r, 0 ≤ r 〈 1/2. Simulation results show that both tests perform satisfactorily.

关键词： general linear model model checking nonignorable missing covariates sensitivity analysis

Surface thermophysical properties on the potentially hazardous asteroid (99942) Apophis

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Research in Astronomy and Astrophysics 2017年第7期17卷 67-76页

作者： Liang-Liang Yu Jianghui Ji Wing-Huen ip Space Science Institute Macao University of Science and Technology CAS Key Laboratory of Planetary Sciences Purple Mountain ObservatoryChinese Academy of Sciences Institute of Astronomy National Central University

We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.

关键词： techniquest hermal infrared -- variables thermal inertia -- asteroid individual (99942)Apophis

A Revisit of the Phobos Events

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空间科学学报 2011年第2期31卷 150-153页

作者： Wing-Huen ip Institutes of Astronomy and Space Sciences National Central UniversityTaiwan Institute of Space Science Macao University of Science and TechnologyMacao

The magnetic field disturbances detected by the Phobos-2 spacecraft in 1989 have been suggested to be caused by a ring of dust and/or gas emitted from the Martian moon,*** physical nature of these"Phobos events"is examined using results from related investigations over the last twenty *** is concluded that there is no clear evidence at present to support the association of magnetic field disturbances in the solar wind with *** situation will be further clarified taking advantage of the multi-spacecraft observations of the Yinghuo-1(YH-1),Mars Express and MAVEN missions beginning in *** is expected that many novel features of solar wind interaction with Phobos(and possibly also Deimos) itself will also be revealed.

关键词： Mars Solar wind interaction Phobos moon Dust rings YH-1

Promoting Transdisciplinary and Transeultural Cooperation In Space Science in Face of COVID-19-Interview with ***-Huen ip,Executive Director of ISSI-BJ

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Bulletin of the Chinese Academy of Sciences 2020年第2期34卷 74-77页

作者：无 Wing-Huen ip BCAS the International Space Science Institute

***-Huen ip,a world-renown scientist in cometary physics,planetary science,solar system evolution and exoplanets,took the post of the Executive Director of the International Space Science Institute一Beijing(ISSI-BJ)in *** the only partner of the well-known International Space Science Institute(ISSI)in Bern outside Switzerland,ISSI-BJ has adopted the same tools as ISSI to facilitate international cooperation and academic exchanges:workshops,forums,and others that rely on in-person communications.

关键词： Director planet outside

Wavelets in probability and statistics——A review in recent advances

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Chinese Science Bulletin 2002年第9期47卷 705-716页

作者： XIE Zhongjie Heung Wong Wai-Cheung ip School of Mathematical Sciences Peking UniversityBeijing 100871China Department of Applied Mathematics The Hong Kong Polytechnic UniversityHong KongChina

The main purpose of this paper is to give a review on recent advances of wavelet in probability and statistics. Many interesting new ideas, new results and new methods are introduced in this review. From many aspects of this paper, probability and statistics researchers may find many new interesting research topics for further studying on wavelets in stochastic processes. New results, such as K- sta-tionarity, wavelet representation of Karhunen processes, hidden periodicities analysis by wavelet approach, hetero-scedasticity in wavelet regression, wavelets and neural networks, etc. are introduced in this paper. Comments, discussions and plentiful references are also involved in this review.

关键词： wavelets K-stationarity time varying spectral analysis nonlinear modeling wavelet variance.

Numerical investigation of wave propagation in the Liverpool Bay,NW England

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Acta Oceanologica Sinica 2011年第5期30卷 1-13页

作者： LI Ming RAYMOND ip WOLF Judith CHEN Xueen BURROWS Richard School of Engineering University of Liverpool Liverpool L69 3GQ UK National Oceanography Centre Joseph Proudman Building Liverpool L3 5DA UK College of Physical and Environmental Oceanography Ocean University of China Qingdao 266100 China

The computer model for near shore wave propagation,SWAN,was used to study wave climates in Liverpool Bay,northwest England with various input parameters,including bottom friction factor,white capping,wind drag formulation and effects of tidal *** were compared with in-situ measurements and reveal the impacts from these inputs on the predictions of wave height and propagation *** particular,the model results were found very sensitive to different input formulations,and tend to underestimate the wave parameters under storm conditions in comparison with the *** is therefore important to further validate the model against detailed field measurements,particularly under large storms that are often of the primary concern.

关键词： coastal engineering flooding wave model near shore tide