Mechanism and Modes of Microbial Minerogenesis of Polymetallic Nodules on the Ocean Floor

This paper presents a quantitative analysis of the relations of the occurrence of polymetallic nodules with the geochemical actions of microbes in the seawater, pore water and sediments at the bottom of the eastern Pacific Ocean basin. Emphasis is laid on the relations of the activity intensity and biochemical transformation rate of aerobic bacteria (iron bacteria, Thiobacillus thioparus, halobacteria and manganese-oxidizing bacteria) and anaerobic bacteria (sulphate-reducing bacteria, denitrifying bacteria, Thiobacillus denitrificans) with mineralization. The experimental research on the migration and accumulation of ore-forming elements caused by microbial and chemical actions shows that the microbes have changed the conditions of oxidation and reduction in the system, and their effect on the element precipitation is much stronger than the chemical actions and accelerates the enrichment of Fe and Mn. It demonstrates that the microbes can change the environment to promote the accumulation of ore-formin     

Numerical Simulation of Strongly Stratified Flow Over a Three-Dimensional Hill

A numerical study of stably stratified flow over a three-dimensional hill is presented. Large-eddy simulation is used here to examine in detail the laboratory experimental flows described in the landmark work of Hunt and Snyder about stratified flow over a hill. The flow is linearly stratified and U/Nh is varied from 0.2 to 1.0. Here N and U are the buoyancy frequency and freestream velocity respectively, and h is the height of the hill. The Reynolds number based on the hill height is varied from 365 to 2968. The characteristic flow patterns at various values of U/Nh have been obtained and they are in good agreement with earlier theoretical and experimental results. It is shown that the flow field cannot be predicted by Drazin's theory when recirculation exists at the leeside of the hill even at UNh 1. The wake structure agrees well with a two-dimensional wake assumption when U/Nh 1 but lee waves start to influence the wake structure as U/Nh increases. The dividing-streamline heights obtained in the simulation are in accordance with experimental results and Sheppard's formula. The energy loss along the dividing streamline due to friction/turbulence approximately offsets the energy gained from pressure field. When lee waves are present, linear theory always underestimates the amplitude and overestimates the wavelength of three-dimensional lee waves. The simulated variations of drag coefficients with the parameterK (=ND/ U) are qualitatively consistent with experimental data and linear theory. Here D is the depth of the tank.     

华北克拉通北缘西段中元古代花岗岩类的特征及其形成构造环境

华北克拉通北缘西段中元古代花岗岩类仅见于查干础鲁－霍尔森构造带以南的雅布赖－巴音诺尔公构造带中，整体上受NEE向长寿命线性构造控制。据岩性可分为斜长花岗岩和石英闪长岩两类。斜长花岗岩为S型花岗岩，但具有向I型过渡的特征，富含Cr,Ni,SiO2,Al2O3，其均值分别为672μg/g，405μg/g,71.40%和14．93％。δEu值变化大，介于0．34和3．95之间，起源于幔源岩浆与壳源物质的混合。石英闪长岩为典型的I型花岗岩，其Cr,Ni含量的均值分别为220μg/g和162μg/g，类似于华南同熔型花岗岩。斜长花岗岩中的锆石U－Pb等时线上交年龄为1256Ma，代表了发生于华北克拉通北缘西段的一次构造－热事件。伴随这一构造－热事件，华北克拉通北缘西段发生拉伸裂解，进入拉张型过渡壳阶段。中元古代花岗岩类是这一构造热事件的重要产物。在这一构造－热事件中，推测查干础鲁－霍尔森一线地壳减薄最大，其北侧的宗乃山－沙拉扎山构造带因无同时代岩浆作用，为非火山型被动陆缘，南侧的雅布赖－巴音诺尔公构造带广泛发育了花岗岩类，镁铁质、超镁铁质侵入岩，以及火山－沉积组合，为火山型被动陆缘，二者构成被动陆缘“对”。     

On the Spectral Moments of Wind Waves

In order to obtain high order spectral moments, the residual moment , as proposed by De-nis, is presented for approximate estimation of spectral moment Glazman's partial averaging idea isdiscussed. It is pointed out that Glazman's method and definition of non-dimensional spectral moment can not be used to es-timate spectral moments for engineering purposes and that method is not supported by theory and computation. The non-dimensional spectral moment of PM spectrum, which should be expressed as is related to wind speed. The0 - 8th moments of PM spectrum are estimated for wind speeds of 10, 20 and 30 m/s and some discussions are given.     

试论我国海岸侵蚀信息系统的建立

本文通过对我国海岸侵蚀特点的分析,阐述了建立海岸侵蚀信息系统的必要性和基本方法,并给出了相应的结论。     

Brief Account of Breakwater Construction in China

-The construction of breakwaters in China in more than 40 years since the founding of the People's Republic of China is reviewed. The construction of two main types of breakwater, upright breakwaters and rubble mound breakwaters, and the way in which they are built are expounded. Recommendations to improve the technology for future breakwater construction are presented.     

Applications of the cyclic spectral analysis to the surface temperature fluctuations in a stochastic climate model and a GCM simulation

Abstract

In this paper, we introduce the cyclostationary processes into climate analysis and undertake a systematic study of the cyclic spectra of surface temperature fluctuations. The technique is adapted from cyclostationarity theory in signal processing. To demonstrate the usefulness of this technique, a very simple cyclostationary stochastic climate model is constructed. Our results show that the seasonal cycle strongly modulates the amplitudes of the covariance and the spectrum. The technique was also applied to the surface temperature fluctuations in a fifteen‐year seasonal run of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM2, R15) using a zonally symmetric all‐land surface as the lower boundary. The results indicate that intraseasonal oscillations localized according to time of year are still present even after the surface temperature fields have been normalized using the commonly used procedure. Both examples suggest that the “annual cycle” cannot be “removed” by simply using a normalization procedure. The climate is not as completely represented when modelled as stationary processes.