黄河口及渤海中南部沉积物工程特性及其机理

采用Ｋａｓｔｅｎ取样器从黄河口及渤海湾中南部海底沉积物中取样，对样品通过土工性质、微结构研究以及粘土矿物分析，阐明本研究区三维空间展布的海底沉积物形成机理及其工程地质规律，论证水动力作用和斜坡不稳定性对工程特性和微结构的重要影响．     

In situ tests for ice strength measurements

Ice effects have caused extensive damage. Enormous forces have been recorded. On the other hand, ice has been used as a structural material under various situations. To use ice beneficially and to assess the danger of ice forces, it is necessary to know the mechanical properties of ice.Results from the large number of ice tests carried out in laboratories show the difficulties of sampling and testing procedures. Most of the tests have not reproduced faithfully enough the conditions existing in nature. To obtain adequate results, laborious and slow samplings and preparations of test specimens have been necessary. Recently, extensive use has been made of in situ tests in order to reduce the number of factors whixh can induce errors in measurements. Large scale tests have simulated actual structures. General ice properties have become available from small-scale in situ tests. Since these tests give rapid results, a large number are already available with a good coverage of field conditions.A theoretical basis has been devised for these in situ tests which measure essentially the unconfined and confined compressive strengths of ice, and practical devices have been developed to execute these tests. A correlation of measurements from laboratory tests and in situ tests has established a link between natural and artificial environments. Brittle elastic and clastic theories have been applied, to find the best correlations for ice tests. Test results have been related to the mechanical properties as used in engineering practice.A very summary conclusion of results is that cold sea ice and cold fresh water ice are both very strong. However, depending on the load rate, ice can be quite brittle, which mitigates dangerous effects from ice action against massive structures.     

Short period internal waves over the Huanghe (Yellow River) delta front

Internal waves with periods of about 5 minutes and trough to crest heights of up to 6.2 m were observed acoustically over the actively accreting delta front of the Huanghe (Yellow River) in the western portion of the Gulf of Bohai, Peoples Republic of China. The radian frequency of the internal waves was close to the locally-observed Brunt-Vaisala frequency. Through the relatively short (one hour) duration of an internal wave train, the amplitude was observed to decrease progressively with time. These internal waves may cause resuspension of delta-front sediments.     

Secondary flow caused by differential roughness,Langmuir circulations,and their effect on the development of sand ribbons

The process of Differential Roughness Secondary Flow (DRSF), hitherto little recognized, recently was demonstrated in a wind tunnel and in a flume. It is suggested here the DRSF may, in the natural environment, play an important part in the persistence and sharp definition of sand ribbons, previously initiated by other processes. In 1980 Karl described a series of sand ribbons, alternating with exposed substrate, which he attributed to the effect of Langmuir circulations. Although Langmuir Circulation Secondary Flow (LCSF) may indeed, in some cases, initiate sand ribbons, the sharply-defined edges typical of these features are explained better by DRSF.     

Mud and fluid migration in active mud volcanoes in Azerbaijan

Mud volcanic eruptions in Azerbaijan normally last for less than a few hours, and are characterized by vigorous extrusion of mud breccias, hydrocarbon gases, and waters. Recent fieldwork and mapping on four active mud volcanoes show that dormant period activity ranges from quiet to vigorous flow of mud and fluids. Geochemical analyses of expelled waters show a wide range in solute concentrations, suggesting the existence of a complex plumbing system. The mud and fluids have a deep origin, but are sometimes stored in intermediate-depth mud chambers. A mixing model between deep-seated saline waters and shallow meteoric water is proposed.     

Nitrate reductase activity and the speciation of selenium at the mouth of Chesapeake bay

Nitrate reductase activity and the concentrations of selenite and selenate were monitored for six months at the mouth of Chesapeake Bay (USA). A positive correlation was found between nitrate reductase activity and the concentration of selenite, suggesting that selenite may be formed in coastal waters and nitrate reductase may be involved in the process.     

Voltammetric estimation of iron(III) thermodynamic stability constants for catecholate siderophores isolated from marine bacteria and cyanobacteria

Thermodynamic stability constants have been estimated for the complexation of iron(III) with catecholate-type siderophores isolated from the marine bacterium Alteromonas luteoviolacea and from the marine cyanobacterium Synechococcus sp. PCC 7002. Stability constants were determined utilizing the “chelate scale” of Taylor et al. (1994). The scale is based upon a linear relationship between the reduction potentials and the pH-independent thermodynamic stability constants for known iron(III) complexes. Log K values for the alterobactin B ferric iron complex are 43.6 ± 1.5 at pH 8.2 and 37.6 ± 1.2 at pH 6, consistent with a shift from bis-catecholate to monosalicylate/monocatecholate iron coordination with decreasing pH. Synechococcus isolates PCC 7002 Nos. 1 and 3 formed iron(III) complexes with stability constants of approximately 38.1 ± 1.2 and 42.3 ± 1.5, respectively. The binding strengths of the iron(III) complexes examined in this study are quite high, suggesting that catecholate siderophores may play a role in the solubilization and biological uptake of iron in the marine environment.     

Digital underwater acoustic voice communications

This paper describes the design of an underwater acoustic diver communication system controlled by a digital signal processor. The speech signal transmission rate is compressed by using linear predictive coding (LPC) and the extracted parameters are transmitted through the water to a synchronized receiver by employing digital pulse position modulation (DPPM). The pulse position in each time frame is estimated by an energy detection and decision algorithm which enables the received LPC parameters to be recovered and used to synthesize the speech signal