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积温能够影响植物的物候期和农业作物的产量及空间分布。在研究中,通常将有限数量站点积温数据外推插值到空间进行分析,在站点空间分布稀疏和地形复杂的地区,积温数据在空间上有较大的不确定性。目前,已有高分辨率的格点化气象数据,在此基础上直接计算可解决上述问题。本研究使用1961—2018年长时间序列的高分辨率格点气温数据（CN05.1）,分析了中国大陆≥0 ℃、≥ 5 ℃、≥10 ℃和≥ 15 ℃的4种积温时空变化,结论如下：① 在中国大陆范围,4种积温的低值区主要分布在青藏高原、新疆天山和中国东北地区,高值区分布在华南地区;② 在58年间,4种积温均表现出显著增加的趋势,尤其以内蒙古和东北地区积温增温趋势显著;③ 这种积温在空间上趋势变化引起了农业区划中热带和亚热带地区面积显著增加,温带和寒温带面积减少;④ 在58年中,4种积温开始时间显著提前,结束时间显著推后。4种积温开始时间转变间隔时间（0~5 ℃、5~10 ℃和10~15 ℃转变所需时间）在黄土高原和内蒙古地区较为剧烈。对于结束时间转变间隔时间,在华中地区趋势变化剧烈。 相似文献
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船舶行为特征挖掘与预测是水上智能交通系统的重要研究内容,也是交通运输工程领域的关键科学问题。为系统研究基于船舶自动识别系统（Automatic Identification System, AIS）数据的船舶行为特征挖掘与预测的研究现状与发展趋势,本文首先针对Web of Science(WOS)和中国知网（China National Knowledge Infrastructure, CNKI）收录的文献,用知识图谱分析软件VOSviewer对文献关键词进行处理,从文献计量学的角度生成高频关键词的聚类图谱和趋势演化。然后对基于AIS数据的水上交通要素挖掘、船舶行为聚类和船舶行为预测3个主题的研究内容、方法、存在问题进行了系统分析和展望,研究结果表明：① 在基于AIS的水上交通要素挖掘方面,主要集中在对AIS数据中表征船舶行为空间特征和交通流的时间特征单独挖掘分析,缺乏对AIS数据的时间、空间以及环境因素特征的关联挖掘,对于如何进行交通要素的关联融合挖掘研究还有待深入探索;② 在船舶行为聚类方面,研究主要是运用无监督聚类方法研究船舶航迹点和航迹段聚类,得到船舶航行行为模式的时空分布和船舶操纵意图辨识模型,然而融合多维特征的船舶轨迹的相似性计算方法、聚类参数的自适应选取以及船舶行为的语义特征建模有待进一步研究;③ 在船舶行为预测方面,主要集中在基于动力学方程、传统智能算法和深度循环神经网络的船舶行为预测研究,考虑船舶行为的随机性、多样性和耦合性的特点,运用混合神经网络模型以及神经网络与向量机、注意力机制相结合的模型实现多维的船舶航行行为特征的实时预测将是新的研究方向。最后提出了基于语义模型的船舶行为特征挖掘、基于深度卷积神经网络的船舶行为的预测和基于知识图谱的船舶行为特征挖掘和预测结果可视化等有待进一步研究的方向。 相似文献
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一种基于里程参数的道路平面几何解析模型 总被引：1，自引：0，他引：1
随着主动安全技术、自动驾驶技术的发展,高精度导航地图得到越来越多的运用。本文提出了一种面向高精度导航地图的、基于里程参数的道路平面几何解析模型。通过动态地构造点集上的正交多项式系和约束最小二乘法,根据拟合最大误差动态地计算道路的几何描述参数。使用该模型进行了120 km高速道路高精度地图数据生产,以三段典型道路为实例进行试验,表明该方法能对道路几何进行准确的描述,保证道路几何的连续与光滑,同时最大限度地减少数据冗余。该模型对高精度地图道路几何描述具有一定优势。 相似文献
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Thermokarst lake is a significant indicator of permafrost degradation. However, the evaluation of thermokarst lake development is very difficult through physical mechanism analysis because the development is influenced by many factors. In the present study, the factors influencing thermokarst lake development were investigated from the perspective of frozen soil and the geographical environment. The influences of six factors on thermokarst lake development in Beiluhe basin, located in the hinterland of the Qinghai–Tibet Plateau, were analyzed: permafrost type, ground temperature, vegetation type, soil type, hydrogeological type, and slope. Sensitivity coefficients were calculated for these factors using statistical methods. The results show that thermokarst lake development was influenced by the analyzed factors as follows: permafrost > soil type > ground temperature > hydrogeological type. Furthermore, 80.1% of the study area was highly sensitive to thermokarst lake development. Overall, thermokarst lake development in the Beiluhe basin was thoroughly evaluated based on sensitivity factors and an established statistical evaluation method. The method detailed in this paper provides a reference for evaluating the likelihood and severity of thermokarst lake development. 相似文献
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手机GNSS芯片可支持多模GNSS观测信号,其提供的原始观测量为高精度导航定位提供了可能,智能手机高精度导航定位成为研究热点之一。本文首先基于自研的反向RTK算法,设计并开发了一套基于智能手机的实时高精度定位系统,降低手机的计算压力;然后基于智能手机小米8,进行了大范围(覆盖深圳、武汉、北京)、多场景(城市开阔/遮挡,高速开阔/遮挡)的动态车载应用测试,用于验证系统的可靠性和可用性。测试结果表明:系统在各场景下均能稳定有效运行,在开阔环境下,小米8可实现亚米级的实时动态定位精度,精度最优可达0.21 m。 相似文献
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《Marine Policy》2017
As the International Whaling Commission has failed to establish a consensus on the interpretation and enforcement of a moratorium on commercial whaling, the disagreement between Australia and Japan over whaling has recently escalated. Australia, a leading opponent of whaling, questioned Japan's scientific whaling program in the Antarctic at the International Court of Justice (ICJ). The ICJ ruled in 2014 that the Japanese whaling program is unscientific, but Japan revised the program and implemented it after the court ruling. To overcome the current international stalemate regarding whaling, this paper examines the possibility of a bargaining solution to this conflict, particularly through voluntary monetary compensation from Australia to Japan to halt whaling activities. The results of nationwide surveys indicate that Australia's total willingness to pay for the discontinuation of whaling by Japan is significantly greater than Japan's willingness to accept to abandon whaling in the high seas despite a substantial population difference between the two countries. The results suggest that a financial transfer could be a win-win strategy to resolve this long-standing international conflict. 相似文献
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This study contributes to solving the problem of how to derive a simplistic model feasible for describing dynamics of different types of ships for maneuvering simulation employed to study maritime traffic and furthermore to provide ship models for simulation-based engineering test-beds. The problem is first addressed with the modification and simplification of a complicated and nonlinearly coupling vectorial representation in 6 degrees of freedom (DOF) to a 3 DOF model in a simple form for simultaneously capturing surge motions and steering motions based on several pieces of reasonable assumptions. The created simple dynamic model is aiming to be useful for different types of ships only with minor modifications on the experiment setup. Another issue concerning the proposed problem is the estimation of parameters in the model through a suitable technique, which is investigated by using the system identification in combination with full-scale ship trail tests, e.g., standard zigzag maneuvers. To improve the global optimization ability of support vector regression algorithm (SVR) based identification method, the artificial bee colony algorithm (ABC) presenting superior optimization performance with the advantage of few control parameters is used to optimize and assign the particular settings for structural parameters of SVR. Afterward, the simulation study on identifying a simplified dynamic model for a large container ship verifies the effectiveness of the optimized identification method at the same time inspires special considerations on further simplification of the initially simplified dynamic model. Finally, the further simplified dynamic model is validated through not only the simulation study on a container ship but also the experimental study on an unmanned surface vessel so-called I-Nav-II vessel. Either simulation study results or experimental study results demonstrate a valid model in a simple form for describing the dynamics of different types’ ships and also validate the performance of the proposed parameter estimation method. 相似文献
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Maintenance and repair at the operational level is a critical function to comply with the standard of competence for officers in charge of an engineering watch in a manned/unmanned ship engine room. The human factor in ship maintenance especially deals with fulfilling of the required competency about dismantling, inspecting, repairing and reassembling equipment in accordance with manuals and good practice stated in STCW Code, as amended in 2010. This study extends the shipboard operation human reliability analysis (SOHRA) through the marine auxiliary machinery maintenance operations. The approach involves the determined marine-specific error producing conditions (EPC) and generic task type parameters to quantify generic error probability (GEP) values along with the subtasks of the maintenance operation. To acquire the EPC and GEP values, the real case study on heavy fuel oil (HFO) purifier overhauling considers different operating conditions on-board selected five ships in a dry bulk fleet. The case study shows that human error probability (HEP) values of tasks in maintenance operation change in regard to ship operating conditions. Consequently, the study contributes to the marine engineering field in improving the human factor in ship repair and maintenance operations. This approach is further extended by incorporating maintenance 4.0 requirements into ship operating environment to conduct scenario-based task analysis. 相似文献
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环境空气污染是一种复杂的非线性动态现象,受道路网络上的交通流、气象条件等因素的影响,定量揭示这些因素与空气污染物浓度的变化关系,是空气质量预测与改善的重要基础。以广东省佛山市南海区气象局空气质量监测站点周边1.5 km的半径区域为研究范围,利用改进后的关联规则算法对监测站点不同方位的道路交通流,引入气象条件,定量分析对空气污染物NO2浓度的影响,并通过线性相关分析验证关联规则的结果。(1)传统的Apriori算法计算效率低,得到的规则多为无效、不可靠。将原算法对数据库多次扫描,改变为对上一频繁K项集的元素进行扫描。并引入新的可靠性衡量指标“提升度”,及加入对关联规则结果的筛选过程。改进后的算法只需扫描数据库一次,新增的两类改进方法使Apriori算法计算效率得到提升,且增强了强关联规则挖掘的可靠性。(2)从强关联规则得出：影响NO2浓度变化的主要因素是风速、温度和气压,风速和温度与NO2浓度的变化呈负相关,气压与NO2浓度变化呈正相关。(3)引入道路交通流,结合气象因素对NO2... 相似文献
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