Localisation and phase transition of acoustic waves in a soft medium containing air bubbles

We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of `phase transition' characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.     

枣庄市农村宅基地管理对策研究

1农村宅基地管理的主要做法（1）枣庄市党委政府重视农民住宅用地问题。该市政府在全市部署开展农村宅基地调查摸底,掌握实情,为市委市政府决策提供依据;同时,在用地指标十分紧张的情况下,从2009年开始对农村宅基地单独下达用地计划,2009年计划下达31.3 hm2,解决农村宅基地问题。市政府要求国土资源部门配合农村住房和危房改造工作,给予用地支持。各区（市）加强组织领导,在政策和财力上支持推进“空心村”治理,一些区（市）分别采取召开现场会等形式进行推广。     

Diagnostic investigation of impulsive pressures induced by plunging breakers impinging on gravel beaches

This paper presents an integrated investigation of physical processes generating impulsive pressures under the action of plunging breakers impinging on gravel beaches. This work is an extension of a recent investigation which suggested that wave impacts from plunging breakers acting on gravel beaches may be a key mechanism to enhance sediment mobilisation. In particular, comparisons of full scale laboratory measurements against model results from a well-validated phase/depth-resolving numerical model based on the Reynolds–Averaged Navier–Stokes (RANS) equations are presented. This represents the first attempt at comparison with such a tool against observed hydrodynamics on steep (slope~1/8) gravel beaches at prototype scale. In order to understand how impulsive pressures are generated under plunging waves, the numerical model is used to carry out a detailed investigation to examine the role of each of the acceleration terms in the momentum balance. Consistent with prior studies, numerical results show that under plunging breakers the local acceleration (∂u/∂t) alone cannot be used as a proxy for pressure gradients. However, the contribution of the third term (w∂u/∂z) of total acceleration is recognized for the first time and indicates that this term has an important role in both the induced pressure gradient and sediment mobilisation as induced by this particular type of breaking. Furthermore, results suggest that a parameterisation of the pressure gradient in terms of ∂u/∂t+u∂u/∂x, may not suffice when dealing with plunging breakers and hence there is a lack of a suitable parameterisation of this process in the present literature. Thus, for different types of breaking it may be necessary to consider a different characterisation of the pressure gradient toward the parameterisation of sediment transport inside the surf zone.     

The THU-NAOC transient survey: the performance and results from the first year

The Tsinghua University-National Astronomical Observatories, Chinese Academy of Sciences(NAOC) Transient Survey is an automatic survey that conducts a systematic exploration of optical transients. This project utilizes a 60/90 cm Schmidt telescope at the Xinglong Station of NAOC. This survey repeatedly covers ～ 1000 square degrees of the northern sky with a cadence of 3–4 d. With an exposure of 60 s,the survey reaches a limiting unfiltered magnitude of about 19.5 mag, which enables us to discover supernovae in their relatively young stages. We describe the overall performance of our survey during the first year and present some preliminary results.     

Sources, pathways and sinks of particulate organic matter in Hudson Bay: Evidence from lignin distributions

Hudson Bay is a large, estuarine, shelf-like sea at the southern margin of the Arctic, where changes in seasonal ice cover and river discharge appear already to be underway. Here we present lignin data for dated sediments from eleven box cores and evaluate sources of terrigenous carbon, transport pathways, and whether terrigenous organic matter has been influenced by recent environmental change. Lignin yields (0.04 to 1.46 mg/100 mg organic carbon) decreased from the margin to the interior and from south to north, broadly reflecting the distribution of river inputs. Lignin compositional patterns indicated distinct regional sources with boreal forest (woody gymnosperm) vegetation an important source in the south, vs. tundra (non-woody angiosperm) in the north. Lignin patterns suggest redistribution of a fine-grained, mineral-associated fraction of the southern-derived terrigenous carbon to the northeast part of the Bay and ultimately into west Hudson Strait with the Bay's cyclonic coastal circulation. A small component of the carbon makes it to the central basins of Hudson Bay but most of the terrigenous organic material in that area appears to derive from resuspension of older, isostatically-rebounding coastal and inner shelf deposits. Most modern plant debris appears to be retained near river mouths due to hydrodynamic sorting, with the exception of the southwest inner shelf, where these materials extend > 30 km from shore. Temporal changes in the composition of terrigenous organic carbon recorded in most of the southern Hudson Bay cores perhaps reflect increases in erosion and cross-shelf transport from coastal deposits, possibly mediated by change in ice climate. In contrast, temporal changes in the northwest may relate to changes in the supply of modern plant debris under recent warmer conditions. On the western shelf, changes may relate to ice climate and the distribution of northern coastal water and/or changes in the delivery of materials by the Churchill River due to water diversion. Although the cores show evidence of change related to the ice climate, there is little evidence that ice itself transports terrigenous organic carbon within the system.     

Vaccination in three different ways against vibriosis of <Emphasis Type="Italic">Seriola dumerili</Emphasis> caused by <Emphasis Type="Italic">Vibrio hollisae</Emphasis>

Bacterin was prepared by formalin-inactivating the virulent strain of Vibrio hollisae isolated from diseased Seriola dumerili （amberjack） suffering from vibriosis. Healthy S. dumeriIi were vaccinated by respective procedures of intramuscular injection, immersion, and orally administration. Results of the three different vaccinations were compared. Blood was drawn from the vaccinated fish every 7 days, and the antibody titers and lysozyme activities of the sera were determined. The antibody titer of injected fish was 1：40 at 7 d, and reached its peak of 1：320 at 28 d, while the fish vaccinated by immersion and orally administration exhibited weak antibody responses, the antibody titres of 〈1：10, 1：20, 1：160 were observed at 7 d, 14 d, 35 d respectively. Compared with the control, the vaccinated fish exhibited significantly higher lysozyme activities （P〈0.05）. Upon challenge with virulent strain, the relative percent survival （RPS） of injected, immersed and oral administrated fish were 75%, 45%, and 40% respectively, and the injected fish showed significantly higher RPS than immersed and oral administrated fish. The results suggested that vaccination of S. dumerili by the injection would be the best strategy to prevent the vibriosis in S. dumerili farm.     

Trade-offs and Synergies of Ecosystem Services in the Taihu Lake Basin of China

Understanding the spatial interactions among multiple ecosystem services is crucial for ecosystem services management. Ecosystem services, including crop production, freshwater supply, aquatic production, net primary production, soil conservation, water conservation, flood regulation, forest recreation, were measured at 1-km grid scale covering the Taihu Lake Basin (TLB) of China. Our objective is to get a comprehensive understanding of the spatial distributions, trade-offs, synergies of multiple ecosystem services across the TLB. Our results found that: 1) majority of ecosystem services were clustered in space and had a similar spatial distribution pattern with the geographical resource endowment. Most of the landscape contributed a high supply of no services, one or two, and a low supply of three to seven services. 2) There were high correlation between forest recreation and freshwater supply and regulating services. Aquatic production had low correlation with other services. 3) The changes of provisioning services led to trade-offs between regulating services and cultural services in the TLB, while synergies mainly occurred among the provisioning service. 4) The spatial relationships of multiple services are consistent at 1-km spatial scale, counties and provinces. This research could help integrate multiple ecosystem services across scales and serve as a reference for decision making.     

准噶尔盆地中部超压封闭层的岩石学特征与封闭机理

本文依据准噶尔盆地中部地区钻井地层压力实测数据,勾画出该区超压顶界面的空间分布形态以及超压封闭层的厚度;重点阐述了2口钻井超压封闭层的岩性构成、成岩作用机理和岩石学与岩石物性特征;通过对比研究,探讨了封闭层的封闭机理。研究表明该区超压顶界面为一个向南倾斜的曲面,横向上可穿过不同的地层层面。超压封闭层由一组砂泥互层的碎屑岩组成,厚度约166～250m,砂岩含量大于50%。砂岩封闭层已达到晚成岩 A_2亚期阶段,自生高岭石、石英次生加大和碳酸盐胶结作用发育,主要与中下侏罗统煤系烃源岩成熟演化过程中排出的大量有机酸溶解铝硅酸岩及其自生矿物有关。封闭层砂岩为致密储层,渗透率<1.0md、孔隙度<10%,由于其内发生了天然气充注,气毛细管封闭成为封闭层的主要封闭机理。     

南亚热带特大型水库浮游植物群落特征及其与环境因子的关系:以新丰江水库为例

为了解亚热带大型深水贫营养水库的浮游植物群落特征及生态现状,2019年9月至2020年8月对新丰江水库的浮游植物群落结构和水体理化指标进行了周年调查.结果 表明,新丰江水库水质达到《地表水环境质量标准》(GB 3838-2002)Ⅰ类标准,综合营养状态指数(TLI(∑))在15～28之间,整体上处于贫营养状态.共检出浮...     

广东区域性暴雨过程的定量化评估及气候特征

利用1961—2017年广东86个地面气象观测站逐日降水资料,定义广东区域性暴雨过程的标准,构建了综合考虑区域暴雨过程持续时间、暴雨范围、最大日降水量和最大过程降水量4个指标的广东区域性暴雨过程综合强度评估方法,由此分析近57年广东区域性暴雨过程次数、强度、雨涝年景等特征和变化。结果表明:近57年来,广东共出现1211次区域性暴雨过程,平均每年21.2次,主要出现在4—9月,单次过程平均持续时间是2.3 d;广东区域性暴雨过程的次数和强度存在明显的月际、年际和年代际变化,次数最多出现在5月,强度最大出现在6月;广东雨涝年景指数以0.17/（10 a）的速率显著上升;强和较强等级的广东区域性暴雨过程次数呈显著增加趋势,较弱等级区域性暴雨次数呈显著减少趋势。评估得到广东强雨涝年有5年:2008年、2001年、1973年、1994年、1993年,其中有4年出现在1990年以后。