Temperature‐ and size‐associated differences in the skeletal structures and osculum cross‐sectional area influence the pumping rate of contractile sponge Cinachyrella cf. cavernosa

Sponges alter the proportion of structural and morphological components such as spicule skeleton and number of oscula in response to environment, development and growth. Such mechanisms indicate morphological and physiological variations within populations. We measured the pumping rate of different sized specimens of contractile sponge Cinachyrella cf. cavernosa present in the intertidal rock pools, during morning and afternoon low tides along the central west coast of India. Additionally, we measured the exhalant opening (oscular cross‐sectional area—OSA), tissue density, spicule skeleton weight and the abundance of choanocyte chambers to assess the morphological variations. Water temperature and sponge size showed a significant positive effect on pumping rate. OSA and the number of oscula increased with sponge size, but the sponge volume‐specific pumping rate did not increase (0.029 ± 0.020 ml/s ml^‐1). Histological sections showed the abundance of chaonocyte chambers increased marginally with the sponge size, but the contraction state affected the count. Both tissue density and spicule skeleton weight were positively correlated with sponge size, particularly the increase in the size and number of spicule bundles radiating from the centre indicated a denser core in larger specimens. The subcortical lacunae and the peripheral choanosome with high abundance of canals appear to be the major volume reduction zones during contraction events. Our results indicate that the size and number of spicule bundles increase with sponge volume and the variation in temperature, contraction state, and size and number of oscula influence the pumping rate of C. cf. cavernosa.     

New expression-based models to estimate scour depth at clear water conditions in rectangular channels

Scouring in the channel contractions occurs due to the flow concentration within them inducing excessive bed shear stress. This is a complex process, so it is difficult to describe it through a general empirical model, the present research work describes contemporary conceptual relationships to estimate the local scour depth under equilibrium and clear water conditions in rectangular channels. Incidentally, gene-expression programming (GEP), evolutionary polynomial regression (EPR), and model tree (MT)-based formulations were utilized to predict the scour depth at long contractions. The input variables comprising average flow velocity, critical threshold velocity of sediment movement, flow depth, median particle diameter, geometric standard deviation, and uncontracted and contracted channel widths were used to feed the applied models. The performances of the developed approach were compared with those calculated using existing scour prediction equations. The results showed that the developed MT approach in terms of linear relationships could predict the scour depth more precisely than GEP, EPR, and the traditional equations. What is more, dimensionless parameter of h₁/b₁ (ratio of upstream flow depth to uncontracted channel width) was determined as the most influential variable in predicting the scour depth in long contractions.     

A method for coupled arch dam‐foundation‐reservoir seismic behaviour analysis

This paper presents a method for coupled arch dam–foundation–reservoir seismic behaviour analysis. The dam is discretized by finite elements (FE) and the foundation and reservoir are discretized by boundary elements (BE). The opening of contraction joints and the spatial variability of the seismic action is taken into account. The study of Pacoima dam by this method is also presented. The computed results show that no cracks were to be expected due to the vibrations induced during the Feb. 9, 1971 San Fernando earthquake. Copyright © 2000 John Wiley & Sons, Ltd.     

Tectonothermal evolution of the gneiss complex at Salur in the Eastern Ghats Grnaulite Belt of India

Textural relations, thermobarometry and petrogenetic grid considerations in the syn-tectonic granitoid massif and the enveloping metasedimentary gneisses at Salur are consistent with a counter-clockwise P–T –t path for the rocks. The low-P/high-T prograde sector is documented by the pre- to syn-D₁ cordierite±orthopyroxene±garnet±spinel–bearing metatexite leucosomes in metapelites. Heating and loading of the rocks (syn- to post-D₁) resulted in the formation of garnet+orthopyroxene± cordierite-bearing diatexites, and decomposition of cordierite in metatexite leucosomes to orthopyroxene+sillimanite+biotite+quartz symplectites. Near-peak temperature, 850 °C at 8.0 kbar, was reached syn- to post-D₂. Post-peak cooling resulted in the stabilization of coronal grossular and anorthite+calcite symplectites at the expense of scapolite+wollastonite+calcite assemblages in calc-silicate gneisses, and the resetting of cation exchange temperatures at 700–750 °C. Near-isothermal decompression at c. 700–750 °C is manifested by the decomposition of garnet porphyroblasts in the granitoid gneisses to plagioclase+orthopyroxene/ilmenite/biotite two-phase coronas and restabilization of cordierite at garnet margins in metapelites. Subsequent low-P, near-isobaric cooling led to the overprinting of granulite facies assemblages by muscovite+calcite assemblages, and further resetting of cation exchange thermometers to lower temperatures c. 600 °C. The tectonothermal evolution of the Salur gneiss complex vis-a-vis the Eastern Ghats Belt is therefore consistent with high degrees of lower crustal melting, followed by prograde heating of the cover rocks due to magma invasion synchronous with crustal compression, and finally thermal relaxation over a protracted period punctuated by tectonic/erosional denudation of the thickened crust.     

A Numerical Investigation of the Eyewall Evolution of a Tropical Cyclone

In this study, a high-resolution numerical simulation is conducted to investigate the eyewall evolution of Typhoon Imbudo (2003). The eyewall contraction, breakdown, and reformation are successfully simulated by the model. The eyewall accordantly shrinks throughout the whole troposphere prior to landfall, while it exhibits di erent variations after landfall in the lower and upper troposphere, respectively. It is found that the dry air advected into the storm inner core through a low-θe channel, the reduced surface latent heat transfer, and the increased in ows in the coastal region are associated with the eyewall contraction.Accompanied with the high-to-low wavenumber change in the vortex Rossby waves, the initial polygonal eyewall transforms to an elliptical one. Such a wavenumber change is likely associated with the change of interaction between the rainbands and the eyewall. The corresponding features of the time-averaged and vertical dynamic and thermodynamic structures are also examined during the storm passage. A tangential wind budget analysis indicates that a strong acceleration due to the contributions of both the eddy and the mean circulation is located in the lower layer in the eyewall during pre-landfall, and the mean circulation contribution to the change in the tendency of the azimuthally averaged tangential wind counteracts the eddy contribution.     

明渠交汇口水流分离区研究

支流汇入主流后,在明渠交汇口下游附近形成分离区,造成过流断面束窄.采用水力学基本理论及试验手段,对等宽明渠交汇口水流分离区的形状及尺寸进行了理论分析和试验研究,提出了分离区收缩系数及能量损失系数的理论表达式并与试验结果进行了比较.研究结果表明,随交汇角或主支流流量相对大小不同,分离区尺寸发生变化;对于给定交汇口几何形状及尺寸,分离区形状基本保持不变,但分离区尺寸随流量比变化并具有较好的相关关系,并随交汇角增大呈有规律增加.     

层状侵入体及其韵律层成因

层状侵入体以其独特的韵律结构记录了岩浆的演化分异过程。围绕韵律层理的成因 ,不同学者提出了很多成层机制 ,归纳起来大体有两类 :一类与岩浆流动和动力成层有关 ,包括流动分异、对流成层、化学成因等 ;另一类为非动力成层机制 ,主要有火成堆积、重力分异、压实作用和固化收缩等观点。影响韵律形成的因素很多 ,通常包括岩浆成分、对流作用、扩散作用、热梯度、氧逸度、温度和压力等。在评述这些成层机制和影响因素的基础上 ,结合攀枝花层状侵入体的特点 ,认为该岩体的韵律结构是在岩浆的固化收缩和压实作用下 ,晶体定向生长和自组织排列的结果 ,是二元 (辉石 ,斜长石 )、固 (岩石 )—液 (岩浆 )相转变系统中动量、能量和物种质量的复杂耦合所形成的分形自组织现象。对层状侵入体的进一步研究应集中在加强实验 (尤其是高温高压实验 )、引入非线性分析以及与成矿研究相结合等方面。     

台风眼壁的云结构与降水形成机制分析

使用带有详细微物理过程的ARPS模式,对台风韦帕（Wipha）进行三重嵌套细网格模拟,利用模式结果,对台风眼壁强降水中心的云结构和降水形成机制进行分析,结果表明：冰相微物理过程是启动和形成台风眼壁暴雨的主要降水形成机制。在9000～14000 m高空,云水在很低的温度下经均质核化产生冰晶,或经非均质核化形成云冰;冰晶通过凝华增长（psfi,贝吉龙过程）、雨水收集云冰产生雪（praci）和冰晶粘附雨水成雪（piacr）过程生长为雪;霰产生主要包括4个过程：冰晶接触雨水使其成霰（piacr）、雪撞冻云水使其成霰（psacr）、雨水收集云冰转化成霰（praci）或雨水冻结为霰（pgfr）;霰粒子通过收集云冰干增长（dgaci）,霰撞冻云滴增长（dgacw）等过程生长;霰融化（pgmlt）和雪融化（psmlt）成雨水后再通过碰并云水等暖云生长过程,最后形成雨水。霰过程的强弱在雨水形成机制中很重要。（29.5°N、121.8°E）和（28.3°N、120.4°E）强降水中心冰晶转化率没有太大差别,但是（29.5°N、121.8°E）强降水中心上空冰晶通过贝吉龙过程快速成长为雪和霰,霰粒子增长过程远远强于（28.3°N、120.4°E）强降水中心,低空又有较高的云水转化率,使降水粒子在暖云中继续快速生长,冷暖云过程的有利配置使（29.5°N、121.8°E）出现较强雨水转化率。     

包含镜射自变量微分方程的遥远概周期解

本文利用遥远概周期函数的基本定义和性质以及Banach压缩映像原理研究了包含镜射自变量微分方程的遥远概周期解问题,证明了遥远概周期解的存在性及唯一性。     

Influences of Different PBL Schemes on Secondary Eyewall Formation and Eyewall Replacement Cycle in Simulated Typhoon Sinlaku (2008)

The effects of different planetary boundary layer (PBL) processes on the secondary eyewall formation (SEF) and eyewall replacement cycle (ERC) in Typhoon Sinlaku (2008) are investigated by using the Weather Research and Forecasting (WRF) model with six different PBL schemes. The SEF and ERC have been successfully simulated with all the six PBL schemes and the mechanism for the SEF and ERC proposed in our previous study has been reconfirmed. It is demonstrated that both the intensification of the storm and the inward-moving outer spiral rainband contribute to the SEF. After the SEF, the associated diabatic heating enhances the secondary eyewall further, and the transfer of moist air from outer region to the primary eyewall is cut off by the secondary eyewall. In such a way, the primary eyewall dies and an ERC completes. It is found that some simulated features of the SEF and ERC, such as the time and location of the SEF and duration of the ERC, do vary from one simulation to another. In order to describe the features of the SEF and ERC quantitatively, a concentric eyewall index (CEI) is defined and a threshold of the CEI is suggested to determine the onset of the secondary eyewall. The differences in the simulated SEF and ERC are discussed and some possible causes are suggested. In addition, based on the CEI threshold and the conservation law of angular momentum, a formula to predict the location of SEF is also proposed and applied to all the six simulations. The success and failure of the formula are then discussed.