横向黏度变化对球层中热对流的影响

本文在常黏度的基础上,加上横向黏度变化,纯粹研究了横向黏度变化对球层中热对流的影响.结果表明,横向黏度变化可以加速或阻碍球层中的热对流,并对球层中热传输方式有调节作用,但是横向黏度变化对球层中热对流的影响会限制在一定的强度范围内,并且难以改变球层中热对流的格局.横向黏度变化所产生的环型场速度占总速度场的比例最多为十几个百分点,难以解释观测到的地表板块运动中的环型场能量大小.     

A review on bivalve shell,a tool for reconstruction of paleo-climate and paleo-environment

Environmental information can be extracted from bivalve shell geochemistry. In this review, the latest research progress and the existing problems as well as the focus of future research on stable oxygen and carbon isotopic composition and trace elemental ratios of bivalve shell were investigated. Oxygen isotopic signatures of bivalve shell have been proved precipitate in equilibrium with their host water and used as a robust tool to reconstruct ancient water temperature. In order to reconstruct quantitative paleo-temperature information, the future research on bivalve shell oxygen isotope should combine with the study of ancient water oxygen isotope. Metabolic effect pre- vents the direct application of stable carbon isotopic composition of bivalve shell from extracting dissolved inorganic carbon information. The contribution of metabolic carbon to bivalve shell is species specific. Stable carbon isotopic composition of dissolved inorganic carbon could be reconstructed if the metabolic contribution could be accounted for. Explore ways to remove contribution of metabolic effects to bivalve shell is the future focus of the research. There is no consensus on the effect of temperature on bivalve trace element ratios, which may be also species spe- cific, each proxy should ideally be validated and calibrated for each species before being used to interpret past climate and environmental conditions. Future research needs to pay attention to the bivalve shell biomineralization process, which controlled bivalve shell trace element ratios. Cultivation experiment is an important way to obtain the relevant conclusions.     

Dynamic Structure-Fluid Interaction Response of a Composite Cylindrical Shell Submerged in Water

This paper analyzes the dynamic structure-fluid interaction response of a submerged compo-site cylindrical shell.Dynamic equations based on the first-order shear deformation theory include the ini-tial stresses and structure-fluid interaction forces due to fluid.The field equation is solved by expandingthe velocity potential into series similar to transverse deflection of the cylindrical shell and thestructure-fluid interaction force is obtained.The dynamic response is investigated by means of series expan-sion method.The effects of structure-fluid interaction on dynamic response are discussed.     

A pseudo-coupled analytic fluid-structure interaction method for underwater implosion of cylindrical shells

Underwater implosion, the rapid collapse of a structure caused by hydrostatic pressure, is a fully coupled, highly dynamic and nonlinear fluid-structure interaction (FSI) problem. The primary motivation behind studying implosion is the short-duration, high-pressure pulse generated in the surrounding water. This paper presents a simplified analytic method to estimate the energy in the pressure pulse, based on potential flow theory. The method accounts for the varying fluid pressure and accompanying FSI. The focus is on long, thin, unstiffened metallic cylindrical shells that collapse in mode 2. The implosion pulse energy is shown to be equal to the maximum system kinetic energy developed during collapse. The kinetic energy is calculated using an energy balance approach and analytic solutions for plastic energy dissipation and energy required to compress the internal air. The time-varying fluid pressure, and subsequently the work done by the fluid on the cylinder, is found using a novel explicit time-stepping methodology. The result is a pseudo-coupled analytic solution for the fluid pressure time history and implosion pulse energy. Solutions for pulse energy agree with RANS numerical simulations within 5%.     

Acoustic radiation from shear deformable ring-stiffened laminated composite cylindrical shell submerged in flowing fluid

Acoustic radiation from a point driven, infinite, periodically ring-stiffened, laminated composite cylindrical shell submerged in flowing fluid is investigated theoretically. Both the effects of in-plane and out-of-plane vibrations of the ring-stiffeners and the effects of fluid convection on far field acoustic radiation behaviors are concerned. The equations of motion of the laminated composite cylindrical shell is presented on the basis of the first order shear deformation theory. Fourier transform and Poisson summation formula are used to transform the equations into a set of infinite algebraic equations expressed in the wavenumber domain. After truncation, the response of the laminated composite cylindrical shell is solved, and the stationary phase approximate is employed to find the expression for the far field sound pressure. Convergence analysis of the numerical solutions is conducted. The theoretical model and numerical method proposed in this paper are validated by comparison with those presented in available literature. Finally, numerical results are presented to demonstrate the effects of various parameters such as the size and spacing of the ring-stiffener, the thickness and the radius of the cylindrical shell, the lamination angle and the lamination scheme of the composite materials as well as the Mach number on the far field sound pressure.     

光照强度对条斑紫菜贝壳丝状体培养的影响

光照与温度对条斑紫菜(Neopyropia yezoensis)贝壳丝状体生长发育与壳孢子放散水平均具有重要影响.因温度对光强的协同效应以及各培养阶段对光强的需求不同,本文仅改变培养光强,研究了不同光照强度对条斑紫菜贝壳丝状体着生、生长、发育及壳孢子放散的影响,为育苗阶段光照强度管理提供数据支撑.在16℃下采用1.3～...     

环肋椭圆柱壳-流场耦合系统自由振动的解析求解方法

提出了分析环肋椭圆柱壳-流场耦合系统自由振动的一种解析求解方法。环肋通过"刚度均摊"到均质椭圆柱壳体上,考虑流场对壳体振动特性的影响,通过Helmholtz方程描述声介质的波动,建立环肋椭圆柱壳-流场耦合系统的自由振动方程,进而求得耦合系统的自由振动固有频率。为了验证方法的准确性,将水下环肋椭圆柱壳退化成水下环肋圆柱壳和不加肋的水下椭圆柱光壳,两个退化模型的计算结果与已有文献结果吻合良好。并详细讨论了椭圆度、环肋间距等主要参数对耦合系统自由振动特性的影响。     

Ecology of Pinnidae (Mollusca: Bivalvia) from the Gulf of Thailand

The ecology of the family Pinnidae was studied by sampling three pinnid species from 36 sampling sites across four different microhabitats in the Gulf of Thailand. The species spatial distributions were mostly uniform, with some populations having random distributions. Species abundances differed between sandy and coral habitats according to non-metric multi-dimension scaling analyses. Although the Gulf of Thailand is a relatively small geographic area, habitats are varied enough to provide variable shell densities. Small islands are important distribution areas, and coral reefs provide both direct and indirect shelter which support high abundances, densities and increased shell size. The highest density was recorded in sand beds within coral reefs. Low density and small shell size in sand beaches might be related to high mortality in shallow water or to adaptations for survival in shallow waters. A clear correlation between sediment composition and species abundance was found in Pinna atropurpurea; abundance increased with the sand content of the sediment. For P. deltodes, abundance increased as the rock fraction of the sediment increased. These results suggest that adaptations in Pinnidae, such as shell size, shell morphology, and the exposure of the shell above the sediment-water interface, are responses for survival in different habitats.     

生物技术清洁生产替代高污染化学法制备甲壳素的研究与应用

从虾壳中分离到一株乳杆菌BR-3,研究发现其最佳发酵起始pH为6.50,最佳培养温度为35℃,在此培养温度下达到对数生长期的时间为42h。采用乳杆菌发酵方法,进行了虾壳制备甲壳素的研究,比较了接种量、葡萄糖加入量、发酵时间等因素对产品质量的影响。结果表明,当接种量为10%、葡萄糖浓度为4.5%、固液比为1︰3、发酵温度为(35±2)℃、发酵时间为3—4d时,平均灰分去除率达95.67%,甲壳素产品灰分含量均小于6%,最低可达1%,产品质量等于或优于传统的酸碱生产方法。发酵液可部分或全部回收,洗涤废水可作下一轮发酵用水,生产废水接近零排放。虾壳乳酸发酵法生产甲壳素是一种清洁生产方法。BR-3培养时间短,培养条件粗放,温度和pH适应范围宽,产酸效率高,残糖少,适合于工业化生产。     

海藻多糖复合胶成膜性研究

以海藻多糖与植物膳食纤维为主要材料,形成一种海藻多糖复合胶(APPC),采用传统硬壳空心胶囊生产的浸沾成型方法,对该复合胶的成膜性能进行了研究。结果表明,当APPC中海藻多糖和植物纤维素的配比度为8:92,成膜胶液的成膜温度在44—48℃,并在该温度下平衡反应0.5—1.5h时,成膜效果较好;形成的APPC膜硬壳空心胶囊的崩解时间为8min;体外药物溶出试验表明APPC膜布洛芬胶囊剂的溶出速率较动物明胶膜相对缓慢,但在30min时的药物溶出度为98.29%,符合国家标准。