基于Item2Vec负采样优化的专题地图产品个性化推荐方法研究     

毛文山  赵红莉  孙凤娇  蒋云钟  姜倩  朱彦儒 《地球信息科学学报》2020,22(11):2128-2139

建立适用于专题地图产品检索的用户偏好推荐模型是提高专题地图质量的有效方式之一,在专题地图产品推荐场景中,存在严重的内容冷启动和评论数据稀疏问题,现有的推荐算法无法为特定类用户推荐不同特征的专题地图产品,导致用户从专题地图中获取偏好信息受到限制。因此,本文构建基于负采样的连续词袋模型和基于Word2Vec的Item2Vec相结合的用户偏好推荐方法,用于专题地图产品推荐。① 计算用户行为日志文件中交互行为数据的隐性评分,以代替专题地图推荐信息流场景中稀疏的用户评论数据;② 基于负采样的连续词袋模型提取目标专题地图的前后地图序列感知特征信息,通过控制正负样本比例为1:2,提升目标专题地图潜在评分的预测精度;③ 通过Item2Vec将带有用户行为特征信息的专题地图映射到向量空间,计算用户对专题地图的相似度矩阵,根据用户偏好程度完成推荐。在构建的专题地图评分实验数据集Thematic CMaps和4个公开验证数据集MovieLens上的测试结果表明:与LFM、Personal Rank、Content Based和SVD 4种传统推荐算法相比,本文所提方法可有效提高潜在评分的预测精度,推荐性能最高达到27.85%;与以霍夫曼采样方式的Item2Vec基础方法和YouTubeNet 2种神经网络推荐算法相比,评分预测精度有一定提高,且推荐性能不断提升,最高达到2.97%和5.78%。以经典算法奇异值分解（SVD）为例,将MovieLens-20M数据集切分后,在数据量不断增大的数据子集中,本文所用方法的评分预测精度和性能均优于SVD方法。  相似文献   

模式降水与温度预报的不一致性特征          下载免费PDF全文

郭达烽  段明铿  夏旻惠  陈翔翔 《应用气象学报》2018,29(3):321-332

为探讨模式产品预报不一致性问题,利用2015年11月—2016年10月业务中常用的GQEC,GQJP及T639模式的12 h降水、2 m温度网格产品,采用跳跃指数定量计算方法,研究了产品在不同区域内跳跃指数变化与预报不一致性问题。结果表明:产品多日平均跳跃指数随预报时效延长而增大;长时效预报比短时效预报跳跃频率大、预报不一致性也大;对比两种要素可知,降水的跳跃指数比温度大,跳跃频率高,预报不一致性大;对比不同模式发现,GQEC不仅跳跃指数值小,且跳跃频率低,预报不一致性小,GQJP虽然跳跃指数值小于T639,但其跳跃频率更高,预报一致性较T639低;产品跳跃频率存在季节差异,夏季降水和温度预报跳跃频率最高而冬季最低,夏季预报不一致性最大。研究还发现:基于跳跃指数的预报不一致性特征与选取的区域大小密切相关,区域越大,跳跃指数和预报不一致性越小;区域内跳跃指数分布特征与地理位置和地形等有关。  相似文献   

基于BPSO-NBayes的雷暴释用预报技术研究   总被引：1，自引：1，他引：0  

刘亚杰  胡邦辉  王学忠  王举  黄泓 《气象科学》2018,38(3):370-377

提出了一种新的雷暴预报法,即二进制粒子群-朴素贝叶斯分类器(Binary Particle Swarm Optimization-Naive Bayesian Classifiers,BPSO-NBayes)方法,以福州、连城、宁波3站为例,对使用T511数值预报产品站点的雷暴释用预报技术进行研究。利用2010—2014年T511数值预报产品和单站观测资料,使用BPSO-NBayes方法,建立了0~72 h雷暴预报模型,并与Fisher判别准则和Bayes判别准则进行比较。预报结果表明,BPSO-NBayes模型临界成功指数都在0.29以上,平均值达到0.33以上,是3种方法中最好的,空报率都在0.59以下,漏报率在0.60以下,而且变化幅度很小。BPSO-NBayes模型明显优于Fisher判别准则和Bayes判别准则,具有良好的稳定性和预报能力。  相似文献   

江西省新一代中短期预报业务流程介绍     

张瑛  许爱华 《气象与减灾研究》2005,28(1):22-24

按照中国气象局以数值预报产品为基础,以MICAPS预报人机交互系统为工作平台的思路．建立了包括气候背景、预报思路、天气会商、预报制作和管理5个模块的江西省新一代中短期预报业务流程,并重点介绍了数据转换、综合图定义、参数修改、网络改造等有关的本地化工作,以及包括天气形势描述、要素预报的人机交互修改、全省实况描述的预报制作和预报产品自动或半自动生成技术。  相似文献   

Potential Impact of Production Chemicals on the Toxicity of Produced Water Discharges from North Sea Oil Platforms   总被引：4，自引：0，他引：4  

S.B. Henderson  S.J.W. Grigson  P. Johnson  B.D. Roddie 《Marine pollution bulletin》1999,38(12):1229-1151

Production chemicals are used on offshore oil production platforms to prevent corrosion and scale formation, and to assist oil–water separation. A proportion of these chemicals may enter the marine environment via the produced water discharge. This study investigated the potential impact of 11 oilfield production chemicals on the toxicity of the produced water discharge. The Microtox® system was used for toxicity assessment of the chemicals, both directly in aqueous preparations and following their partitioning between oil (crude and low toxicity mineral base oil) and North Sea brine. For the majority of the chemicals tested, the toxicity of the aqueous phase to the test organism following partitioning against crude oil, was not significantly altered by the presence of process chemicals when used in their normal field dosage concentrations. However, there was evidence that certain chemicals could increase the partitioning of oil components into the aqueous phase by an order of magnitude, when applied at high dosage concentrations.  相似文献   

Primary Product Distributions from the Reaction of OH with m-, p-Xylene, 1,2,4- and 1,3,5-Trimethylbenzene     

D. F. Smith  T. E. Kleindienst  C. D. McIver 《Journal of Atmospheric Chemistry》1999,34(3):339-364

A study was conducted to examine the OH-initiated degradation products of the four title compounds in the presence of sub-part-per-million levels of NO_x. The oxidation was conducted in a dynamic reactor to minimize the conversion of the aromatic compounds. The experiments were designed to represent reaction pathways that occur in the atmosphere at ambient NO₂ concentrations. A wide range of ring-retaining and ring-cleavage products having widely varying yields were measured during the study. For m-xylene, the major primary products observed (with molar yields) were methyl glyoxal (0.40), 4-oxo-2-pentenal (0.12), glyoxal (0.079), and m-tolualdehyde (0.049). For p-xylene, the major primary products were p-tolualdehyde (0.103), 2,5-dimethylphenol (0.13), cis-3-hexene-2,5-dione (0.176), trans-3-hexene-2,5-dione (0.045), 2-methyl-butenedial (0.071), glyoxal (0.394), and methylglyoxal (0.217). Several other reaction products were measured at yields less than 3%. The primary products for OH + 1,2,4-trimethylbenzene were found as follows: methylglyoxal (0.44), glyoxal (0.066), cis-3-hexene-2,5-dione (0.13), trans-3-hexene-2,5-dione (0.031), biacetyl (0.114), 3-methyl-3-hexene-2,5-dione (0.079), and 2-methyl-butenedial (0.045). Six other (ring retaining) products were measured at yields less than 3%. The primary products for OH + 1,3,5-trimethylbenzene were methylglyoxal (0.90), 3-methyl-5-methylidene-5(2H)-furanone (0.1), 3,5-dimethyl-3(2H)-2-furanone (0.1), 3,5-dimethyl-5(2H)-2-furanone biacetyl (0.08), and 2-methyl-4-oxo-2- pentenal (0.05). Three other products were detected at molar yields less than 5%. In some cases, the yields for the ring fragmentation products could only be based on calibrations from surrogate compounds. Yields for several of the unsaturated dicarbonyl compounds have not been reported previously while yields for methylglyoxal, glyoxal, and biacetyl are largely consistent with previous reports. Some of the primary furanone products are the identical to those reported as secondary products in aromatic systems.  相似文献   

三峡地区气候Z-R关系     

张家国  王佐兵  力梅  杨洪平  万玉发  蔡宏 《气象》1999,25(3):44-48

在三峡地区降水条件气候均匀区域划分的基础上,用Ａｔｌａｓ一阶矩概率匹配法,分别在每一个区域建立了对流型、雷雨混合型、阵雨混合型３种雨型随测距变化的气候Ｚ－Ｒ关系。这些关系能综合订正由波束平均作用、雨区对电磁波的衰减等因素所造成的雷达测量降水的误差  相似文献   

海洋生态产品价值实现的参与主体演化博弈分析     

史亚平  朱庆林 《海洋通报》2023,(5)

海洋生态产品价值实现对推进海洋生态文明建设与海洋经济高质量发展具有重要意义。目前,海洋生态产品价值实现存在市场化程度不高、公众参与度低、实现不充分等问题。本文通过构建海洋生态产品价值实现参与主体（企业、政府和社会公众）的演化博弈模型,探究各方主体的策略稳定性规律,探讨三方博弈系统的均衡点及其稳定性,并运用Matlab仿真分析不同参数变化对系统演化的影响,最后依据博弈分析结果为探索“政府＋市场”的海洋生态产品价值实现路径提供对策建议。结果表明,政府是海洋生态产品价值实现的引导者与推动者,管控成本和社会收益是影响其策略选择的主要因素,加强政府的奖惩力度、增加企业提供海洋生态产品的潜在收益、降低供给成本对企业参与海洋生态产品价值实现具有正向作用,社会公众购买海洋生态产品所获效用的提升与监督成本的减少有利于促进社会公众参与海洋生态产品价值实现。  相似文献   

Consistency of precipitation products over the Arabian Peninsula and interactions with soil moisture and water storage     

Youssef Wehbe  Marouane Temimi  Dawit T. Ghebreyesus  Adam Milewski  Hamid Norouzi  Elsy Ibrahim 《水文科学杂志》2018,63(3):408-425

The regional-scale consistency between four precipitation products from the GPCC, TRMM, WM, and CMORPH datasets over the Arabian Peninsula was assessed. Their macroscale relationships were inter-compared with soil moisture and total water storage (TWS) estimates from AMSR-E and GRACE. The consistency analysis was studied with multivariate statistical hypothesis testing and Pearson correlation metrics for the period from January 2000 to December 2010. The products and GRACE estimates were assessed over a representative sub-domain (United Arab Emirates) with available in situ well observations. Next, geographically temporally weighted regression (GTWR) was employed to examine the interdependencies among the peninsula’s hydrological components. The results showed GPCC-TRMM recording the highest correlation (0.85) with insignificant mean differences over more than 90% of the peninsula. The highest GTWR predictive performance of TWS (R² = 0.84) was achieved with TRMM forcing, which indicates its potential to monitor changes in TWS over the arid peninsular region.  相似文献   

新型抗水氯氧镁水泥防渗渠在自然环境的水化产物、相转变规律及其对强度的影响          下载免费PDF全文

石天阳  余红发  麻海燕  李颖 《盐湖研究》2021,29(3):38-46, 55

氯氧镁水泥(Magnesium oxychloride cement, MOC)具有快凝、早强、高强、防火和不腐蚀玻璃纤维等优点,非常适合于制作玻璃纤维增强薄壁制品,在农业灌溉工程中具有良好的应用前景。采用XRD和TOPAS分析了新型抗水氯氧镁水泥制成内蒙古防渗渠的物相组成,探讨了氯氧镁水泥制品在自然环境的水化产物与相转变规律、以及相组成对强度的影响。结果表明,在水分缺少的条件下,氯氧镁水泥的水化产物主要为5Mg(OH)_2·MgCl_2·8H_2O(5·1·8)和Mg(OH)_2;在水分充足的条件下,水化产物主要为Mg(OH)_2和5·1·8,碳化产物为碳化氯氧化镁Mg(OH)_2·MgCl_2·2MgCO_3·6H_2O(1·1·2·6)和水菱镁矿4MgCO_3·Mg(OH)_2·4H_2O(4·1·4)。水化产物对强度有促进作用,而碳化产物会降低强度。通过10年的工程环境考验,证明新型氯氧镁水泥制品在环境中能够保持主要强度相5·1·8的稳定性,具有良好的长期力学性能。  相似文献