排序方式: 共有32条查询结果,搜索用时 453 毫秒
1.
There is a need to obtain the hydrologic data including ocean current,wave,temperature and so on in the South China Sea.A new profiling instrument which does not suffer from the damage due to nature forces or incidents caused by passing ships,is under development to acquire data from this area.This device is based on a taut single point mid-water mooring system.It incorporates a small,instrumented vertically profiling float attached via an electromechanical cable to a winch integral with the main subsurface flotation.On a pre-set schedule,the instrument float with sensors is winched up to the surface if there is no ship passing by,which is defined by an on-board miniature sonar.And it can be immediately winched down to a certain depth if the sonar sensor finds something is coming.Since,because of logistics,the area can only be visited once for a long time and a minimum of 10 times per day profiles are desired,energy demands are severe.To respond to these concerns,the system has been designed to conserve a substantial portion of the potential energy lost during the ascent phase of each profile and subsequently use this energy to pull the instrument down.Compared with the previous single-point layered measuring mode,it is advanced and economica1.At last the paper introduces the test in the South China Sea. 相似文献
2.
介绍了 2 0 0 0年度上海天文台卫星激光测距观测和系统的改进情况 相似文献
3.
中国在美洲OFDI的基本特征与决定因素 总被引:6,自引:2,他引:4
利用2004-2014年中国在OFDI(Outward Foreign Direct Investment, 对外直接投资)的4616家企业数据,分析了其行业结构特征、地理分布特征及其变动,建立了东道国的属性特征和东道国—母国的关系特征相融合的OFDI区位决定模型,定量识别了中国在美洲OFDI的国别决定因素及其行业间差异。研究发现:① 中国在美洲OFDI的国家分布高度集中,行业主体是服务业,国有企业为主导投资者,私营企业投资地位不高。但随时间推移,国家分布趋于离散,制造业地位提升、服务业地位下降,私营企业比重上升。② 国内制造业企业是中国在美洲OFDI的投资主体,且投资行业高度集中于批发零售、商务服务、进出口贸易,这是制造业企业构建国际价值增长链,参与全球化的客观表现,印证了其逐步且连续的国际扩张历程。与制造业公司向服务领域的延伸不同,进出口贸易公司、商务服务公司侧重于原有主营业务优势的拓展。③ 关系变量的引入,有效提升了OFDI国家差别的解释力度。出口显著促进了OFDI,符合互补模型的表现,预示着中国在美洲的OFDI仍处于熟悉海外市场的初始阶段。在这一阶段,良好且紧密的政治社会关系能有效促进OFDI,并且民间力量的推动逊色于国家力量的推动。④ 中国在美洲的OFDI,市场寻求动机最为明显,能源获取动机、技术获取动机、降低生产成本的动机,没有获得模型的充分确认。⑤ 与批发零售业、商务服务业、制造业追求市场规模的共性不同,地质勘查与开发业更侧重于资源寻求,并由此决定了良好政治关系以及国有企业的特殊重要性。 相似文献
4.
5.
6.
7.
8.
9.
叙述了新研制成功的以8751单片机为主体的23位光轴角度编码器电路的原理,电路接口和程度实现,23位编码器的分辨率为0' ,155.同时它能以度,分,秒为单位显示望远镜的指向(高度,方位)显示精度为1'。新的23位编码器电路结构简洁,性能可靠,完全达到了事先的设计要求并已正常用在激光测路仪上。 相似文献
10.
Modeling sediment transport depends on several parameters, such as suspended sediment concentration (SSC), shear stress, and settling velocity. To assess the ability of Pulse-Coherent Acoustic Doppler Profiling (PC-ADP) to non-intrusively quantify spatial and temporal SSC and settling velocity at seabed, a field experiment was conducted in the Beibu Gulf (Tonkin Gulf), in the South China Sea. The spatial profiles and temporal variations in SSC at 1 m above bottom were derived from PC-ADP acoustic backscatter intensity determinations after being calibrated with the optical backscatter sensor (OBS) measurements at the same elevation. The PC-ADP and OBS results agreed well. The temporal settling velocity obtained from Rouse profiles agreed well with the Soulsby formula based on size information by LISST (laser in situ scattering and transmissometry). Tides and tidal currents are diurnal in the gulf. SSC increased with increasing ebb and flood flow, and it rapidly decreased with the increase of distance from the seabed. The maximum SSC at 0.16 m and 1.3 m above bottom reached 816 mg/L and 490 mg/L during spring tides, respectively. The sediments consisted of mineral particles 23-162 μm in diameter and 0.05-2.04 cm/s in settling velocity. Generally, both the SSC and settling velocity followed variations in the bottom friction. Results suggest that PC-ADP is able to provide reasonable SSC and settling velocity measurements of both profiles and time series for a long study period. 相似文献