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101.
102.
大黄鱼皮肤溃烂病病原的研究 总被引:3,自引:0,他引:3
从福建省厦门西海域某渔排养殖大黄鱼(Pseudosciaena cyogga)患皮肤溃烂病的肝脏、肌肉分离到2株优势菌。人工感染试验证实其中1株为致病菌。该菌的主要生理生化特性为革兰氏阴性,短杆状,极生单鞭毛,发酵葡萄糖,氧化酶阳性,赖氨酸脱羧酶、鸟氨酸脱羧酶阳性,精氨酸脱羧酶、水杨素、枸橼酸盐阴性,不产生H2S,利用葡萄糖、甘露醇产酸,对O/129(10μg)不敏感。在含0%,10%NaCl的普通培养基上不生长;在含2%,4%,6%,8%NaCl的普通培养基中生长;在温度30,35,40℃下生长良好,但4℃不生长。初步鉴定该病原菌为副溶血弧菌(Vibrio parahaemolyticus)。药敏试验表明,该菌对卡那霉素、复方新诺明、链霉素等10种药物敏感,对青霉素G、氨苄青霉素、利福平等6种药物不敏感。 相似文献
103.
Effect of Cyclic Loading Frequency on Undrained Behaviors of Undisturbed Marine Clay 总被引:2,自引:0,他引:2
Based on a series of cyclic triaxial tests, the effect of cyclic frequency on the undrained behaviors of undisturbed marine clay is investigated. For a given dynamic stress ratio, the accumulated pore water pressure and dynamic strain increase with the number of cycles. There exists a threshold value for beth the accumulated pore water pressure and dynamic strain, below which the effect of cyclic frequency is very small, but above which the accumulated pore water pressure and dynamic strain increase intensely with the decrease of cyclic frequency for a given number of cycles. The dynamic strength increases with the increase of cyclic frequency, whereas the effect of cyclic frequency on it gradually diminishes to zero when the number of cycles is large enough, and the dynamic strengths at different frequencies tend to the same limiting minimum dynamic strength. The test results demonstrate that the reasons for the frequency effect on the undrained soil behaviors are beth the creep effect induced by the loading rate and the decrease of sample effective confining pressure caused by the accumulated pore water pressure. 相似文献
104.
The motion and the drift force of a floating OWC (oscillating water column) wave energy device in regular waves are studied taking account of the oscillating surface-pressure due to the pressure drop across the duct of the air chamber. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine-type Green function while the outer problem with the Kelvin-type Green function. The added mass, wave damping and excitation coefficients as well as the motion and drift force of the OWC device are calculated for various values of parameter related to the pressure drop. 相似文献
105.
根据1986—1990中美热带西太平洋海气相互作用8个航次合作综合调查资料,分析了1987年10月赤道中西太平洋165°E(10°N-6°S)次表层水形成溶解氧最大值的原因。1986-1987年E1Nino衰退时期,该海域赤道附近在E1Nino强盛时期下沉的次表层水开始回升,短时期内形成了类似于中、高纬度海域的理化环境,使浮游生物在混合层内聚集生长,最终导致溶解氧含量在次表层出现最大值和过饱和含量。 相似文献
106.
Fayun Liang Mingyi Zhao Chengrui Qin Yajie Jia Zhongwei Wang Guiping Yue 《Marine Georesources & Geotechnology》2020,38(1):114-121
AbstractThe construction of a 100-km road network is planned on a land reclamation area in the Oujiang Estuary in China. The embankment had a height of 4 m and a base width of 60 m. The reclamation area is newly filled by a 3-m dredger fill on a 48-m thick layer of marine clay. Estimation of the settlement of the future road network is difficult. To guide the construction of the road network, a 1/100-scale centrifuge model test was performed with a marine clay sample from the construction site to simulate the layered settlements and evaluate the drainage effect of prefabricated vertical drains in the dredger fill in the following 10 years. The results of the centrifuge modeling test are verified by 10-month in situ monitoring, which shows agreement between the centrifuge modeling test results and the in situ results. The test results indicate that additional time is needed to reinforce the newly added dredger fill by the surcharge preloading method to uplift the elevation of the reclamation area with dredger fill. 相似文献
107.
AbstractThe scour phenomena around vertical piles in oceans and under waves may influence the structure stability. Therefore, accurately predicting the scour depth is an important task in the design of piles. Empirical approaches often do not provide the required accuracy compared with data mining methods for modeling such complex processes. The main objective of this study is to develop three data-driven methods, locally weighted linear regression (LWLR), support vector machine (SVR), and multivariate linear regression (MLR) to predict the scour depth around vertical piles due to waves in a sand bed. It is the first effort to develop the LWLR to predict scour depth around vertical piles. The models simulate the scour depth mainly based on Shields parameter, pile Reynolds number, grain Reynolds number, Keulegan–Carpenter number, and sediment number. 111 laboratory datasets, derived from several experimental studies, were used for the modeling. The results indicated that the LWLR provided highly accurate predictions of the scour depths around piles (R?=?0.939 and RMSE = 0.075). Overall, this study demonstrated that the LWLR can be used as a valuable tool to predict the wave-induced scour around piles. 相似文献
108.
AbstractThe ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design. 相似文献
109.
研究了2003年10月采于珠江口5个站位的沉积物剖面酸挥发性硫化物(AVS)和同时提取的重金属(SEM:Pb,Zn,Cu,Cd,Ni)。其中,站位1、2位于中滩,其沉积物的AVS含量变化范围较小,为0.25—4.06μmol.g-1;站位3、4位于西滩,其沉积物的AVS含量变化范围较大,为0—26.09μmol.g-1。中滩和西滩沉积物的AVS含量均随深度增加。西滩表层沉积物的AVS含量接近于零,这可能与该水域较强的底层流和沉积物的再悬浮作用有关。站位5位于珠江口外侧,其表层沉积物的AVS含量相对较高,且垂向变化较小,可能是还原性沉积物间歇性再悬浮后重新沉积的结果。站位1、2和5沉积物中同时提取的重金属含量大体在0.95±0.2μmol.g-1范围内,随深度增加略呈下降趋势;而西滩沉积物重金属含量相对较高,为1.43—2.42μmol.g-1,且在一定深度范围内随深度增加呈明显下降的趋势,表明珠江口西滩沉积物中的重金属污染有加重的趋势。对AVS/SEM摩尔比值和单个金属的毒性效应研究显示,珠江口内尤其是西滩的表层沉积物存在重金属污染,对其中生活的底栖生物具有潜在的毒性效应。 相似文献
110.
Environmental control of growth and BChl a expression in an aerobic anoxygenic phototrophic bacterium, Erythrobacter longus (DSMZ6997) 总被引:1,自引:0,他引:1
1Introduction Aerobic anoxygenic phototrophic bacteria(AAPB) are facultative heterotrophs that can utilizelight for photosynthesis. These unique-functioningbacteria are widely distributed in marine environ-ments, such as coastal waters (Shiba et al., 1991… 相似文献