利用超快速精密星历约束的北斗卫星实时精密定轨     

范磊  施闯  李敏 《大地测量与地球动力学》2018,38(9):937-942

以广播星历为起算轨道的北斗卫星实时滤波精密定轨往往需要较长收敛时间，针对此，提出利用超快速精密星历约束的实时精密定轨方法。通过MGEX跟踪网全球分布的51个测站连续7 d的实测数据，利用平方根信息滤波对北斗卫星实时精密轨道进行确定，并以3 d解事后轨道作为参考，评估北斗卫星实时滤波轨道精度。结果表明，利用广播星历作起算轨道时，北斗实时滤波轨道平均需要经过15 h收敛才能达到稳定，而新方法在这段时间内轨道变化较为平稳，未出现明显的收敛现象，并且7 d时间内GEO卫星在切向、法向和径向上RMS分别优于2.5 m、20 cm和30 cm，IGSO和MEO卫星在3个方向上分别优于30 cm、15 cm和10 cm。
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基于高斯两步移动搜寻法的村镇避难场所可达性研究     

但文羽  肖映辉  胡周灵  詹庆明 《地球信息科学学报》2018,20(10):1412-1421

避难场所可达性是指避难场所与受灾居民之间的通达性,即灾害发生时,避难人员通过避难疏散通道到达避难场所的难易程度,是评价避难场所布局合理性的重要指标。本研究结合高斯两步移动搜寻法和网络分析法,从供需双向出发对村镇地区避难场所进行可达性分析。2种方法的结合,既充分考虑了需求点与设施点的相互作用,又充分考虑了设施点的吸引力随距离的衰减关系,并基于实际道路,以步行疏散时间作为搜索半径,降低了传统研究中因忽略供需间相互作用及实际距离而引起的可达性结果的误差。最后,以神农架松柏镇区为例,验证该方法的实际应用价值。结果表明,该方法能够有效测定村镇地区避难场所的空间可达性,同时,基于GIS软件可以直观地揭示研究区域内避难场所可达性空间分布差异。该方法可为制定科学的村镇防灾减灾规划提供方法支持。  相似文献   

基于GIS的石家庄市雾霾分析     

苏亚聪  史娟  徐爽 《北京测绘》2020,(2):233-237

为了得出雾霾气象成因机制、影响因素和时空分布特征,以石家庄市区与郊县为研究区域,将2013年9月至2016年12月石家庄市各市区、郊县的PM2.5历史监测数据中的有效数据进行了数据分析处理得到雾霾浓度数据,还有温度、降水、风速、地形和人口密度等数据,运用GIS分析的方法,模拟绘制石家庄雾霾的时空分布图、雾霾与各影响因子的专题对比图,得到雾霾形成机制的因子、雾霾的时空分布规律、雾霾季节变化特征、雾霾与地形间的关系等;运用数据分析软件OriginPro8.SR3分析雾霾浓度与风速数据、降雨数据、温度数据间的相关性。  相似文献   

解郁安神法联合体外反搏对PCI术后气滞血瘀型胸痹患者的临床疗效观察          下载免费PDF全文

王敏  徐新利  姜光萍 《应用海洋学学报》2020,36(12):1

目的：观察解郁安神法联合体外反搏（EECP）对经皮冠状动脉介入治疗（PCI）术后气滞血瘀型胸痹患者的临床疗效。方法：将80例冠心病PCI术后气滞血瘀型胸痹患者随机分为治疗组和对照组,每组各40例。对照组采用PCI术后规范化治疗,同时联合EECP治疗;治疗组在对照组基础上加服解郁安神方治疗,随访观察7周,比较2组临床证候疗效、Zung焦虑自评量表（SAS）评分、抑郁自评量表（SDS）评分、西雅图心绞痛调查量表（SAQ）评分。结果：总有效率治疗组为82.5%（33/40）,高于对照组的60.0%（24/40）,2组比较,差异有统计学意义（P<0.05）;2组SAS、SDS、SAQ评分治疗前后组内比较及治疗后组间比较,差异均有统计学意义（P<0.05）。结论：解郁安神法联合EECP治疗可明显改善PCI术后气滞血瘀型胸痹患者的临床症状,缓解焦虑抑郁程度,提高患者生活质量,值得临床推广应用。  相似文献   

Wave energy conversion under constrained wave-by-wave impedance matching with amplitude and phase-match limits     

《Applied Ocean Research》2019

This paper investigates an approach to limit the fullness of ‘tuning’ provided by wave-by-wave impedance matching control of wave energy devices in irregular waves. A single analytical formulation based on the Lagrange multiplier approach of Evans [1] is used to limit the velocity amplitude while also limiting the closeness of the phase match between velocity and exciting force. The paper studies the effect of the present technique in concurrently limiting the device velocity and the required control/actuation force. Time domain application requires wave-profile prediction, which here is based on a deterministic propagation model. Also examined in the time domain is the effect of possible violation of the displacement constraint, which for many designs implies impacts at hard stops within the power take-off mechanism. Time domain simulations are carried out for a 2-body axisymmetric converter (with physical end-stops) in sea states reported for a site off the US east coast. It is found that the approach leads to effective power conversion in the less energetic sea states, while as desired, considerable muting of the optimal response is found in the larger sea states. Under the assumptions of this work, the end-stop collisions are found to have a minor effect on the power conversion. The present approach could be used to guide the design of power take-off systems so that their displacement stroke, maximum force, and resistive and reactive power limits are well-matched to the achievable performance of a given controlled primary energy converter.  相似文献   

Wave tank and bench-top control testing of a wave energy converter     

《Applied Ocean Research》2019

An increasing number of experiments are being conducted to study the design and performance of wave energy converters. Often in these tests, a real-time realization of prospective control algorithms is applied in order to assess and optimize energy absorption as well as other factors. This paper details the design and execution of an experiment for evaluating the capability of a model-scale WEC to execute basic control algorithms. Model-scale hardware, system, and experimental design are considered, with a focus on providing an experimental setup capable of meeting the dynamic requirements of a control system. To more efficiently execute such tests, a dry bench testing method is proposed and utilized to allow for controller tuning and to give an initial assessment of controller performance; this is followed by wave tank testing. The trends from the dry bench test and wave tank test results show good agreement with theory and confirm the ability of a relatively simple feedback controller to substantially improve energy absorption. Additionally, the dry bench testing approach is shown to be an effective and efficient means of designing and testing both controllers and actuator systems for wave energy converters.  相似文献   

Overview of In - Situ Biodegradation and Enhancement     

DONG Jun  Anthony Adzomani  Zhao Yongsheng 《世界地质(英文版)》2002,5(1)

Microbial degradation technologies have been developed to restore ground water quality in aquifers polluted by organic contaminants effectively in recent years. However, in course of the degradation, the formation of biofilms in ground water remediation technology can be detrimental to the effectiveness of a ground water remediation project. Several alternatives are available to a remedial design engineer, such as Permeable Reactive Barriers (PRBs) and in -situ bioremediation, Hydrogen Releasing Compounds (HRCs) barrier, Oxygen Releasing Compounds (ORCs) barrier etc. which are efficient and cost- effective technologies. Excessive biomass formation renders a barrier ineffective in degrading the contaminants, Efforts are made to develop kinetics models which accurately determine bio - fouling and bio - filn formation and to control excessive biomass formation.  相似文献   

Muon density measurements with the KASCADE central detector     

《Astroparticle Physics》2002,16(4):183-386

Frequency distributions of local muon densities in high-energy extensive air showers (EAS) are presented as signature of the primary cosmic ray energy spectrum in the knee region. Together with the gross shower variables like shower core position, angle of incidence, and the shower sizes, the KASCADE experiment is able to measure local muon densities for two different muon energy thresholds. The spectra have been reconstructed for various core distances, as well as for particular subsamples, classified on the basis of the shower size ratio N_μ/N_e. The measured density spectra of the total sample exhibit clear kinks reflecting the knee of the primary energy spectrum. While relatively sharp changes of the slopes are observed in the spectrum of EAS with small values of the shower size ratio, no such feature is detected at EAS of large N_μ/N_e ratio in the energy range of 1–10 PeV. Comparing the spectra for various thresholds and core distances with detailed Monte Carlo simulations the validity of EAS simulations is discussed.  相似文献   

Discovery of 13 New Variable Stars in the Field of the Open Cluster NGC 2168 （M35）     

Juei-Hwa Hu  Wing-Huen Ip 《中国天文和天体物理学报》2005,5(4):356-362

A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars.  相似文献   

Revisiting Sustainable Development of Dry Valleys in Hengduan Mountains Region   总被引：5，自引：1，他引：4  

TANGYa XIEJiasui SUNHui 《山地科学学报》2004,1(1):38-45

Dry valleys are a striking geographic landscape in Hengduan Mountains Region and are characterized by low rainfall, desert type of vegetation and fragile environment. Past efforts and resources have been concentrated mainly on rehabilitation of degraded ecosystem and fragile environment, particularly reforestation, while socio-economic development has been largely overlooked. Despite successes in pocket areas, the overall trend of unsustainability and environmental deterioration are continuing. It is important to understand that uplift of the Tibetan Plateau is the root cause of development of dry valleys, and development and formation of dry valleys is a natural process. Human intervention has played a secondary role in development of dry valleys and degradation of dry valleys though human intervention in many cases has speeded up environmental degradation of the dry valleys. It is important to understand that dry valleys are climatic enclaves and an integrated approach that combines rehabilitation of degraded ecosystems and socio-economic development should be adopted if the overall goal of sustainable development of dry valleys is to be achieved. Promotion of niche-based cash crops, rural energy including hydropower, solar energy, biogas and fuelwood plantation is recommended as the priority activities.  相似文献