Analysis of the land surface heterogeneity and its impact on atmospheric variables and the aerodynamic and thermodynamic roughness lengths

The land surface heterogeneity has a very significant impact on atmospheric variables (air temperature T-a, wind speed u, and humidity q), the aerodynamic roughness length z(0m), thermodynamic roughness length z(0h), and the excess resistance to heat transfer kB(-1). First, in this study the land surface heterogeneity has been documented through the comparison of surface reflectance r(0), surface temperature T-0, net radiation flux R-n, and sensible heat flux H partitioning over the different land cover types in the experimental areas of the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment on the Tibetan Plateau (GAME/Tibet), the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project on the Tibetan Plateau (CAMP/Tibet), the Heihe Basin Field Experiment (HEIFE), the Arid Environment Comprehensive Monitoring Plan, 95 (AECMP' 95), and the Dun Huang Experiment (DHEX). The results show that the surface heterogeneity was very significant in the areas of the HEIFE, the AECMP' 95, and the DHEX and that it was less significant in the areas of CAMP/Tibet and GAME/Tibet. Second, the vertical profiles of T-a, u, and q in the near-surface layer and above the blending height z(b) have been analyzed using the atmospheric boundary layer (ABL) tower data, radiosonde data, and tethered balloon data observed during the HEIFE, the DHEX, and the CAMP/Tibet. The results show that the land surface heterogeneity leads in the near-surface layer to different vertical profiles of u, T-a, and q overlying the surfaces of the Gobi and the oasis in the areas of the HEIFE and DHEX. The values of u, T-a, and q become well mixed above a height of about 300 m at the HEIFE and 150 m at the DHEX. z(0m), z(0h), and kB(-1) over the different land surfaces have also been determined in this study. The results show that the land surface heterogeneity leads to different aerodynamic and thermodynamic parameters over the areas of the HEIFE, the AECMP' 95, and the GAME/Tibe

(A-LIEP 2011): Internationalization and Collaboration: The Case of the Hong Kong Library Association / Leo F.H. Ma and Venia Y.M. Mak

The Hong Kong Library Association was established in 1958 by a few enthusiastic librarians in Hong Kong. Over its 53-year history, it has emerged into a unique library and information professional body, engaging local librarians from all sectors, while also having a global reach. This paper gives a brief overview of the history of the Association and its major developmental stages. In the past two decades, the Association has been actively advocating for the library profession both regionally and internationally. From the perspective of Greater China, the Association has been serving as a ―bridge‖ to facilitate communication between library associations in Mainland China, Taiwan and Macau. In response to the fast changing library scene in the Asia-Pacific region, this paper points out that the Association can play a more active role by collaborating more closely with regional library associations and societies. The Association can also provide more consultancy services to help professionalizing the library associations of developing countries in South East Asia. Apart from mounting international and regional conferences, the Association has attempted to collaborate with other professional bodies, such as the former IEE (HK) Management Section and the Evergreen Education Foundation, in order to foster international cross-disciplinary co-operation. This paper also highlights the increasingly diversified needs of the Association‘s membership and the major challenges encountered by the Association which - unlike many other library associations in the region - is not a publicly funded organization. This paper also discusses the possibilities of reviewing the role and structure of the Council of the Association, in order to meet these challenges in the global era

Predicting new superhard phases

The search for new superhard materials is of great importance in view of their major roles played for the fundamental science and the industrial applications. Recent experimental synthesis has made several great successes, but the synthetic difficulty in general remains. Materials design technique is greatly desirable as a request to assist experiment. In this paper, two rational theoretical methods of design of superhard materials have been reviewed: (i) substitutional method, which is successful in some cases, but limited to the known chemically related phases, and (ii) global free energy minimization method, which can be applied to large scale of materials with the only information of chemical compositions. The successful applications have been described and the main principles are summarized.Пошуки нових надтвердих матеріалів дуже важливі як з погляду їх ролі для фундаментальної науки, так і промислового застосування. Нещодавно було проведено декілька дуже успішних експериментів синтезу, однак труднощі синтезу загалом збереглися. Для допомоги в експериментах дуже потрібна техніка проектування матеріалів. У даній статті розглянуто два раціональні теоретичні методи дизайну надтвердих матеріалів: (1) метод заміщення, який є успішним у деяких випадках, але обмежується відомими хімічно спорідненими фазами, і (2) метод глобальної мінімізації вільної енергії, який може бути застосований до великої кількості матеріалів при наявності тільки інформації про хімічний склад.Поиски новых сверхтвердых материалов очень важны как с точки зрения их роли для фундаментальной науки, так и промышленного применения. Недавно было проведено несколько очень успешных экспериментов синтеза, однако трудности синтеза в общем сохранились. Для помощи в экспериментах нужна техника проектирования материалов. В данной статье рассмотрены два рациональных теоретических метода дизайна сверхтвердых материалов: (1) метод замещения, который является успешным в некоторых случаях, но ограничивается известными химически родственными фазами, и (2) метод глобальной минимизации свободной энергии, который может быть применен к большому количеству материалов при наличии только информации о химических составах

Investigation of Ultrasonic Assisted Friction Stir Spot Welding of Magnesium Alloy to Aluminum Alloy

A new welding method: ultrasonic assisted friction stir spot welding (UAFSSW) was put forward in the present study. UAFSSW was successfully applied to weld dissimilar AZ31 Mg alloy and 6061 Al alloy. Results show that for either conventional FSSW or UAFSSW, sound joints are obtained in the configuration of upper Mg alloy and lower Al alloy. Ultrasonic vibration is beneficial to the upward flow of lower aluminum alloy, the increase of the stir zone (SZ) width and the refinement of the grains in the SZ. All cross sections of the Al–Mg joints exhibit the formation of intermetallic compounds (IMC) in the SZ. The crack of the conventional FSSW joint propagates exactly along the interface between the dissimilar materials and presents an inverted “V” morphology. After reaching the highest point of the hook defect, crack of the UAFSSW joint extends to the keyhole, leaving a portion of Mg alloy on the lower sheet. Conventional FSSW joint and UAFSSW joint show different IMC compositions at the faying interface

A nonlinear hydrodynamical approach to granular materials

We propose a nonlinear hydrodynamical model of granular materials. We show how this model describes the formation of a sand pile from a homogeneous distribution of material under gravity, and then discuss a simulation of a rotating sandpile which shows, in qualitative agreement with experiment, a static and dynamic angle of repose.Comment: 17 pages, 14 figures, RevTeX4; minor changes to wording and some additional discussion. Accepted by Phys. Rev.

The dependence of the EIT wave velocity on the magnetic field strength

"EIT waves" are a wavelike phenomenon propagating in the corona, which were initially observed in the extreme ultraviolet (EUV) wavelength by the EUV Imaging Telescope (EIT). Their nature is still elusive, with the debate between fast-mode wave model and non-wave model. In order to distinguish between these models, we investigate the relation between the EIT wave velocity and the local magnetic field in the corona. It is found that the two parameters show significant negative correlation in most of the EIT wave fronts, {\it i.e.}, EIT wave propagates more slowly in the regions of stronger magnetic field. Such a result poses a big challenge to the fast-mode wave model, which would predict a strong positive correlation between the two parameters. However, it is demonstrated that such a result can be explained by the fieldline stretching model, \emph{i.e.,} that "EIT waves" are apparently-propagating brightenings, which are generated by successive stretching of closed magnetic field lines pushed by the erupting flux rope during coronal mass ejections (CMEs).Comment: 11 pages, 8 figures, accepted for publication in Solar Phy

Diurnal and inter-monthly variation of land surface heat fluxes over the central Tibetan Plateau area

The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study. The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed

Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and νp nucleosynthesis processes

© 2018 The Authors. Published by Elsevier B.V. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of 82Zr and 84Nb were measured for the first time with an uncertainty of ∼10 keV, and the masses of 79Y, 81Zr, and 83Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr–Nb cycle in the rp-process unlikely. The new proton separation energy of 83Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus 84Sr relative to the neutron-deficient molybdenum isotopes in the previous νp-process simulations.Peer reviewe

Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure