Xylem anatomy and hydraulic conductivity of three co-occurring desert phreatophytes     

A. RzepeckiF. Zeng  F.M. Thomas 《Journal of Arid Environments》2011,75(4):338-345

The tree species Populus euphratica, the shrub Tamarix ramosissima and the sub-shrub Alhagi sparsifolia are phreatophytes that grow along the southern fringe of the Taklamakan Desert (NW China). We hypothesised that in the shoot xylem of these species, the fraction of conduits with a large cross-sectional area and the hydraulic conductivity decrease in the sequence A. sparsifolia > T. ramosissima > P. euphratica according to the different ground water distances at the typical sites of the species’ occurrence. The theoretical hydraulic conductivity related to the total cross-sectional xylem area (k_ttot) or to the cross-sectional area of the conduits (k_tcond) was computed using a modified Hagen-Poiseuille equation. The percentage of wide conduits and k_tcond were highest in A. sparsifolia, and smallest, in P. euphratica. With regard to k_ttot, the diffuse-porous to semi-ring-porous P. euphratica occupied an intermediate position due to an increased percentage of conducting area related to the total cross-sectional xylem area. This figure as well as k_ttot were lowest in the semi-ring-porous to ring-porous T. ramosissima. The k_ttot values corresponded to the leaf area-related hydraulic conductivity calculated from measurements in the field. Altogether, our results match the typical occurrence of the species with respect to the ground water depth.  相似文献   

船只目标SAR、HFSWR和AIS多手段融合探测的点迹关联分析   总被引：3，自引：1，他引：2  

纪永刚  张杰  孟俊敏  王祎鸣 《海洋学报(英文版)》2014,33(9):73-81

A space-borne synthetic aperture radar （SAR）, a high frequency surface wave radar （HFSWR）, and a ship automatic identification system （AIS） are the main remote sensors for vessel monitoring in a wide range. These three sensors have their own advantages and weaknesses, and they can complement each other in some situations. So it would improve the capability of vessel target detection to use multiple sensors including SAR, HFSWR, and A/S to identify non-cooperative vessel targets from the fusion results. During the fusion process of multiple sensors＇ detection results, point association is one of the key steps, and it can affect the accuracy of the data fusion and the efficiency of a non-cooperative target＇s recognition. This study investigated the point association analyses of vessel target detection under different conditions： space- borne SAR paired with AIS, as well as HFSWR, paired with AIS, and the characteristics of the SAR and the HFSWR and their capability of vessel target detection. Then a point association method of multiple sensors was proposed. Finally, the thresholds selection of key parameters in the points association （including range threshold, radial velocity threshold, and azimuth threshold） were investigated, and their influences on final association results were analyzed.  相似文献   

Stress analysis of top tensioned riser under random waves and vessel motions     

Xiaomin Li  Haiyan Guo  Fanshun Meng 《中国海洋大学学报(英文版)》2010,9(3):251-256

The bending stresses of top tensioned riser(TTR)under combined excitations of currents, random waves and vessel motions are presented in this paper, and the effect of the internal flowing fluid on the riser stresses is also considered. The computation programs which are used to solve the differential equations in the time domain are compiled and the principal factors of concern including the angular movements at the upper and lower ends of the riser, lateral displacements and bending stresses are presented. Then the effects of current velocity, random wave, top tension, vessel mean offset, low frequency motion and internal flow velocity on the bending stresses of the riser are analyzed in detail.  相似文献   

Dynamic responses of top tensioned riser under combined excitation of internal solitary wave, surface wave and vessel motion     

GUO Haiyan  ZHANG Li  LI Xiaomin  LOU Min 《中国海洋大学学报(英文版)》2013,12(1):6-12

An investigation on the dynamic response of a top tensioned riser (TTR) under combined excitation of internal solitary wave, surface wave and vessel motion is presented in this paper. The riser is idealized as a tensioned slender beam with dynamic boundary conditions. The KdV-mKdV equation is chosen to simulate the internal solitary wave, and the vessel motion is analysed by using the method proposed by Sexton. Using finite element method, the governing equation is solved in time domain with Newmark-β method. The computation programs for solving the differential equations in time domain are compiled and numerical results are obtained, including dimensionless displacement and stress. The action of internal solitary wave on the riser is like a slow powerful impact, and is much larger than those of surface wave and vessel motion. When the riser is under combined excitation, it vibrates at frequencies of both surface wave and vessel motion, and the vibration is dominated by internal solitary wave. As the internal solitary wave crest passes by the centre of the riser, the maximum displacement and stress along the riser occur. Compared to the lower part, the displacement and stress of the riser in the upper part are much larger.  相似文献   

Uptake and biological effects of synthetic glucocorticoids in common carp (Cyprinus carpio)     

Kei Nakayama  Yoshiyuki Inoue  Naomi Ikeda  Naoki Hashizume  Hidekazu Murakami  Takeshi Ishibashi  Hirofumi Ikeda  Tomohiko Isobe  Shin-Ichi Kitamura  Go Suzuki 《Marine pollution bulletin》2014

Uptake and biological effects of synthetic glucocorticoids (GCs) were analyzed using common carp (Cyprinus carpio). Fish were exposed to clobetasol propionate (CP) or clobetasone butyrate (CB) individually or in mixture at 1 μg L⁻¹ for 21 days. Bioconcentration factor (BCF) of CB was calculated as 100, and BCF of CP was less than 16. No effects were found in fish erythrocyte and leukocyte numbers and serum glucose levels after exposure to the selected GCs. On the other hand, serum concentrations of free amino acids significantly increased in GC-exposed groups. Thus, exposures to synthetic GCs at relatively low concentrations seemed to cause enhancement of protein degradation and subsequent increase of serum free amino acids without a corresponding increase in serum glucose levels, an effect which might be related to partial induction of gluconeogenesis by GC.  相似文献   

Assessing the suitability of commercial fisheries data for local-scale marine spatial planning in South Africa     

《African Journal of Marine Science》2013,35(4):467-480

This study integrates fisheries logbook data with observer and vessel monitoring system (VMS) data in order to assess the accuracy of reported data and to develop high-resolution spatial data suitable for use in local-scale marine spatial planning analyses. Spatial assessments were conducted on five nearshore commercial fisheries to provide baseline information to inform spatial management and conservation planning in Algoa Bay, South Africa. Clear spatial patterns in the distribution of fishing effort were apparent for the linefishery, chokka-squid and inshore demersal trawl sectors. Observer and VMS data confirmed the broad spatial distribution of resource-use patterns of logbook data. Combining these data sources allowed higher-resolution spatial indices of fishing effort to be developed, which are suitable for systematic spatial planning on a local scale and can be used for future spatial management and conservation.  相似文献   

氧化铁矿物作为环境材料在土壤和水体中的应用   总被引：4，自引：0，他引：4  

陈静 《贵州地质》2001,18(3):205-209

本文简要介绍了氧化铁矿物的基本性能和应用领域，着重阐述了氧化铁矿物在土壤改良和治理土壤中重金属有毒元素和水体污染中的应用，明确提出氧化铁矿物作为环境矿物材料储量大、提取简单、治理污染设备简易且效果好、无二次污染，展望了氧化铁矿物在控制和保护环境领域中的应用前景。  相似文献   

船姿分析及其对多波束测量的影响   总被引：4，自引：0，他引：4  

赵建虎  刘经南  张红梅 《武汉大学学报(信息科学版)》2001,26(2):144-149

根据船体操纵性和耐波性理论，结合船姿实验数据，分析了姿态参数的外界受动因素。考虑船姿对多波束测量的影响，结合多波束测量原理，分析了不同姿态对坐标的影响，给出了相应的坐标计算和误差影响数学模型，最后姿态测量误差对测深的影响，结合IHO测深规定，计算出了不同姿态测量的精度指标；分析了姿态测量误差对条带拼接的影响，并提出了相应的解决方法。  相似文献   

上海青浦福泉山遗址出土石器的岩石类型与特征     

程之牧 《上海国土资源》1993,(1):26-34

青浦县福泉山古文化遗址,经本市考古工作者的多年发掘,从崧泽文化与良渚文化墓葬群中出土了一批石制生产工具和礼器,其中包括斧、钺、(石奔)、凿,矢、刀、铲、镰刀、三角形大刀、锥形器及砺石(磨刀石)等共计10余种。这批工具主要由变质岩类与岩浆岩类岩石磨制而成。选用石料质地坚硬,加工精美,说明5000年前的上海先民,已具有颇高的智慧与创造力。  相似文献   

南非沿海异常风浪及其对船舶航行的影响     

刘涛 《气象科技》2006,34(6):792-795

南非沿海低压强烈发展时常伴随着异常天气的发生,风向由东北风转为西南风,波浪情况也变的较为复杂。这种异常的风浪对船舶的航行安全影响极大。通过对这种异常风浪的分析,结合船舶气象导航的具体工作列举了一个具体的个例,给出船舶经过该海域时应以避让为主,密切注意周围站点的气压场和风场的变化,一旦遇到恶劣的天气和海况时应根据具体情况选择最佳的避风场所。  相似文献